docs(language_server): add contribute guide for oxc_language_server (#709)

Author: Sysix

.vitepress/config/en.ts

@@ -258,6 +258,7 @@ export const enConfig = defineLocaleConfig("root", {
               link: "/docs/contribute/transformer",
             },
             { text: "Minifier", link: "/docs/contribute/minifier" },
+            { text: "Language Server", link: "/docs/contribute/language_server" },
             { text: "VSCode", link: "/docs/contribute/vscode" },
           ],
         },

src/docs/contribute/language_server.md

@@ -0,0 +1,49 @@
+---
+title: Language Server
+outline: deep
+---
+
+This page tells you the main concept of the `oxc_language_server` and what the differences to the CLI are.
+If you want to learn more about the communication between the language server and the editor, the official [LSP/LSIF documentation](https://microsoft.github.io/language-server-protocol/) is a great start.
+The [`README.md`](https://github.com/oxc-project/oxc/blob/main/crates/oxc_language_server/README.md) of the language server has a quick overview of the relevant specs.
+
+Note: In this document we will talk a lot about "tools", this is an abstract concept of the core logic for `oxlint` and `oxfmt`.
+
+## `oxc_language_server` concept of implementing tools
+
+`oxc_language_server` can be used to upgrade your own script with the capability to work as a language server.
+The server on its own does not change your files or create suggestions. This is the responsibility of the tool.
+Instead, it manages the workspace folders and all the communication for loading the right configuration.
+To communicate with the provided tools, the server provides a [`ToolBuilder` and `Tool` trait](https://github.com/oxc-project/oxc/blob/main/crates/oxc_language_server/src/tool.rs).
+
+## Difference between Language Server and CLI
+
+### Editors changes the file, server communicates the changes
+
+A small but important part about the communication of a file and the fix of it.
+The CLI Tools are writing the changes to the file system.
+The (oxc) language server should NEVER write to it, instead it just communicates it changes to the editor.
+
+### Workspace Folders
+
+You know when you open a git project in the editor? That is a workspace folder. The LSP has the concept of opening multiple (git) projects at the same time.
+Each of the projects can have its own configuration (see next part), but the most important part is the own "context" with a workspace URI.
+You can think of a workspace URI as the same as a "current working directory" for the CLI tool.
+Keep in mind that a workspace folder can be added / removed by the editor.
+
+### Configurations (with folders)
+
+The language server can (like the CLI flags) be configured, the oxc language server follows the concept:
+Each workspace folder can have its own configuration. As an example: git project A uses type aware linting, git project B uses dangerous fixes on auto save.
+
+### Changing Configuration
+
+Surprise! The user can change the language server configuration on the fly. The editor will send us the updated configuration.
+Currently, the server will send each tool the old and new configuration, so it can handle all kinds of stuff.
+Depending on the configuration the tool can restart/rebuild itself.
+
+### Watch Patterns & Changing watched files
+
+Your tool can tell the editor to watch for specific file (glob) patterns and notify the server, when the file is changed/created/deleted.
+This is mostly used for the `.ox**rc.json` configuration and the referenced files inside of it (example `extends` from `oxlint`).
+Depending on the configuration of the workspace and the tool, the tool may need to restart/rebuild itself again.