Docs: add instructions for Herb language server (#2610)

Author: ocarreterom

docs/src/language_servers.md

@@ -705,6 +705,27 @@ There are multiple options:
     }
     ```
 
+### Herb
+1. Install the `herb-language-server` package (see [github:marcoroth/herb](https://github.com/marcoroth/herb))
+
+    ```sh
+    npm install -g @herb-tools/language-server
+    ```
+
+2. Open `Preferences > Package Settings > LSP > Settings` and add the `"herb"` client configuration to the `"clients"`:
+
+    ```jsonc
+    {
+        "clients": {
+            "herb": {
+                "enabled": true,
+                "command": ["herb-language-server", "--stdio"],
+                "selector": "text.html.rails"
+            }
+        }
+    }
+    ```
+
 ## Rust
 
 Follow installation instructions on [LSP-rust-analyzer](https://github.com/sublimelsp/LSP-rust-analyzer).