docs: Add initial language settings documentation (#6957)

This pull request implements the following documentation changes:

- [x] Copy existing language settings docs from old docs repo
- [x] Add new pages for Zig, Haskell, Gleam, Deno and PureScript
- [x] Add `rust-analyzer` target directory section to Rust language page

Release Notes:

- Added initial language settings documentation
([#4264](https://github.com/zed-industries/zed/issues/4264)).

docs/src/languages/cpp.md

@@ -0,0 +1,4 @@
+# C++
+
+- Tree Sitter: [tree-sitter-cpp](https://github.com/tree-sitter/tree-sitter-cpp)
+- Language Server: [clangd](https://github.com/clangd/clangd)