feat(parser): add Elixir language support

- [x] Add Elixir documentation extraction (@doc and @moduledoc attributes)
- [x] Add Elixir symbol extraction (modules, functions, macros, structs, protocols)
- [x] Add tree-sitter Elixir language parser integration
- [x] Add Elixir language detection for .ex and .exs file extensions
- [x] Add Elixir symbol extraction tests
- [x] Update language support table in README
- [x] Improve install script with package manager detection and LSP installation
- [x] Fix shell script portability (replace echo -e with printf)
- [x] Fix checksum verification in install script for macOS/Linux compatibility

internal/server/server.go

@@ -670,6 +670,8 @@ func languageToExtension(language string) string {
 		return ".c"
 	case "cpp", "c++":
 		return ".cpp"
+	case "elixir":
+		return ".ex"
 	default:
 		return ""
 	}