feat: configurable left and right language text

## Details

Allow users to configure text to add around the language border using
`code.language_left` and `code.language_right`. This surrounds the main
section, remainder continues to be filled with `code.language_border`.

Some example configurations are:

```lua
require('render-markdown').setup({
    code = {
        language_border = '▃',
        language_left = '🭃',
        language_right = '🭎',
    },
})
```

```lua
require('render-markdown').setup({
    code = {
        language_border = ' ',
        language_left = '',
        language_right = '',
    },
})
```

```lua
require('render-markdown').setup({
    code = {
        language_border = '▄',
        language_left = '█',
        language_right = '█',
    },
})
```

Author: MeanderingProgrammer

README.md

@@ -467,6 +467,10 @@ require('render-markdown').setup({
         border = 'hide',
         -- Used above code blocks to fill remaining space around language.
         language_border = '█',
+        -- Added to the left of language.
+        language_left = '',
+        -- Added to the right of language.
+        language_right = '',
         -- Used above code blocks for thin border.
         above = '▄',
         -- Used below code blocks for thin border.
@@ -1084,6 +1088,10 @@ require('render-markdown').setup({
         border = 'hide',
         -- Used above code blocks to fill remaining space around language.
         language_border = '█',
+        -- Added to the left of language.
+        language_left = '',
+        -- Added to the right of language.
+        language_right = '',
         -- Used above code blocks for thin border.
         above = '▄',
         -- Used below code blocks for thin border.

doc/render-markdown.txt

@@ -532,6 +532,10 @@ Default Configuration ~
             border = 'hide',
             -- Used above code blocks to fill remaining space around language.
             language_border = '█',
+            -- Added to the left of language.
+            language_left = '',
+            -- Added to the right of language.
+            language_right = '',
             -- Used above code blocks for thin border.
             above = '▄',
             -- Used below code blocks for thin border.
@@ -1143,6 +1147,10 @@ Code Block Configuration ~
             border = 'hide',
             -- Used above code blocks to fill remaining space around language.
             language_border = '█',
+            -- Added to the left of language.
+            language_left = '',
+            -- Added to the right of language.
+            language_right = '',
             -- Used above code blocks for thin border.
             above = '▄',
             -- Used below code blocks for thin border.

lua/render-markdown/config/code.lua

@@ -14,6 +14,8 @@
 ---@field min_width integer
 ---@field border render.md.code.Border
 ---@field language_border string
+---@field language_left string
+---@field language_right string
 ---@field above string
 ---@field below string
 ---@field inline_left string
@@ -113,6 +115,10 @@ M.default = {
     border = 'hide',
     -- Used above code blocks to fill remaining space around language.
     language_border = '█',
+    -- Added to the left of language.
+    language_left = '',
+    -- Added to the right of language.
+    language_right = '',
     -- Used above code blocks for thin border.
     above = '▄',
     -- Used below code blocks for thin border.
@@ -155,6 +161,8 @@ function M.validate(spec)
     spec:type('min_width', 'number')
     spec:one_of('border', vim.tbl_values(Border))
     spec:type('language_border', 'string')
+    spec:type('language_left', 'string')
+    spec:type('language_right', 'string')
     spec:type('above', 'string')
     spec:type('below', 'string')
     spec:type('inline_left', 'string')

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.5.7'
+M.version = '8.5.8'
 
 function M.check()
     M.start('version')

lua/render-markdown/render/markdown/code.lua

@@ -32,14 +32,17 @@ function Render:setup()
     end
     local widths = self.node:widths()
     local width = vim.fn.max(widths)
+
     local language = self:offset(self.config.language_pad, width)
     local left = self:offset(self.config.left_pad, width)
     local right = self:offset(self.config.right_pad, width)
-    local body = math.max(
-        widths[1] + language,
-        left + width + right,
-        self.config.min_width
-    )
+
+    local body = str.width(self.config.language_left)
+        + str.width(self.config.language_right)
+        + language
+        + widths[1]
+    body = math.max(body, left + width + right, self.config.min_width)
+
     self.data = {
         language = language,
         padding = left,
@@ -120,20 +123,24 @@ function Render:language(info, language, delim)
         border_hl = colors.bg_as_fg(border_hl)
     end
 
-    local body = self:line()
+    local text = self:line()
     if self.config.language_icon and icon then
-        body:text(icon .. ' ', language_hl)
+        text:text(icon .. ' ', language_hl)
     end
     if self.config.language_name then
-        body:text(language.text, language_hl)
+        text:text(language.text, language_hl)
     end
     if self.config.language_info then
-        body:text(info.text:sub(#language.text + 1), info_hl)
+        text:text(info.text:sub(#language.text + 1), info_hl)
     end
-    if body:empty() then
+    if text:empty() then
         return false
     end
 
+    local left = self:line():text(self.config.language_left, border_hl)
+    local right = self:line():text(self.config.language_right, border_hl)
+    local body = left:extend(text):extend(right)
+
     local border = border_hl and self.config.language_border or ' '
     local width = self.data.body - delim.start_col
 

lua/render-markdown/types.lua

@@ -97,6 +97,8 @@
 ---@field min_width? integer
 ---@field border? render.md.code.Border
 ---@field language_border? string
+---@field language_left? string
+---@field language_right? string
 ---@field above? string
 ---@field below? string
 ---@field inline_left? string