Add missing code block lang (#1795)

Author: Kissaki

book/coming_from_bash.md

@@ -4,7 +4,7 @@
 If you're coming from `Git Bash` on Windows, then the external commands you're used to (e.g, `ln`, `grep`, `vi`, etc) will not be available in Nushell by default unless you have already explicitly made them available in the Windows Path environment variable.
 To make these commands available in Nushell as well, add the following line to your `config.nu` with either `append` or `prepend`.
 
-```
+```nu
 $env.Path = ($env.Path | prepend 'C:\Program Files\Git\usr\bin')
 ```
 :::

book/configuration.md

@@ -450,7 +450,7 @@ In other words, **_variable arguments are not allowed for parser keywords_**.
 
 However, Nushell creates some convenience _constants_ that can be used to help identify common file locations. For instance, you can source a file in the default configuration directory using:
 
-```
+```nu
 source ($nu.default-config-dir | path join "myfile.nu")
 ```
 

book/environment.md

@@ -103,7 +103,7 @@ $env.FOO? | default "BAR"
 
 Alternatively, you can check for the presence of an environmental variable with `in`:
 
-```
+```nu
 $env.FOO
 # => BAR
 

book/how_nushell_code_gets_run.md

@@ -24,7 +24,7 @@ Of course, this runs as expected using `nu hello.nu`. A similar program written
 
 In _"interpreted languages"_ code usually gets handled something like this:
 
-```
+```text
 Source Code → Interpreter → Result
 ```
 

book/operators.md

@@ -58,7 +58,7 @@ Presented in descending order of precedence, the article details the operations
 - Assignment operations
 - Logical not (`not`)
 
-```
+```nu
 3 * (1 + 2)
 # => 9
 ```

book/variables.md

@@ -202,7 +202,7 @@ Using [filter commands](/commands/categories/filters.html) with immutable variab
 
 Variable names in Nushell come with a few restrictions as to what characters they can contain. In particular, they cannot contain these characters:
 
-```
+```text
 .  [  (  {  +  -  *  ^  /  =  !  <  >  &  |
 ```
 

book/working_with_tables.md

@@ -574,7 +574,7 @@ With no arguments, the output rendered from the `table` command will often _disp
 
 This can be useful when you need to store the rendered view of structured data as a string. For example, to remove all ANSI formatting (colors) from a table:
 
-```
+```nu
 ls | table | ansi strip
 ```
 

contributor-book/plugin_protocol_reference.md

@@ -1311,7 +1311,7 @@ Most messages are encoded in the same way as their JSON analogue. For example, t
 
 is encoded in the MessagePack format as:
 
-```
+```text
 81                   // map, one element
   a5 "Hello"         // 5-character string
   83                 // map, three elements

cookbook/files.md

@@ -48,7 +48,7 @@ Output
 
 Suppose you have a file with the following format.
 
-```
+```text
 band:album:year
 Fugazi:Steady Diet of Nothing:1991
 Fugazi:The Argument:2001

cookbook/setup.md

@@ -53,7 +53,7 @@ Note: if you've never used `vim` before and you want to leave typing `:q!` will
 
 Go to the end of the file and add
 
-```
+```nu
 $env.EDITOR = vim
 ```