lsp: Retrieve links to documentation for the given symbol (#19233)

Closes #18924 

Release Notes:

- Added an `editor:OpenDocs` action to open links to documentation via
rust-analyzer

crates/proto/proto/zed.proto

@@ -276,6 +276,7 @@ message Envelope {
 
         LanguageServerPromptRequest language_server_prompt_request = 268;
         LanguageServerPromptResponse language_server_prompt_response = 269;
+
         GitBranches git_branches = 270;
         GitBranchesResponse git_branches_response = 271;
 
@@ -293,7 +294,10 @@ message Envelope {
         GetPanicFiles get_panic_files = 280;
         GetPanicFilesResponse get_panic_files_response = 281;
 
-        CancelLanguageServerWork cancel_language_server_work = 282; // current max
+        CancelLanguageServerWork cancel_language_server_work = 282;
+        
+        LspExtOpenDocs lsp_ext_open_docs = 283;
+        LspExtOpenDocsResponse lsp_ext_open_docs_response = 284; // current max
     }
 
     reserved 87 to 88;
@@ -2024,6 +2028,17 @@ message LspExtExpandMacroResponse {
     string expansion = 2;
 }
 
+message LspExtOpenDocs {
+    uint64 project_id = 1;
+    uint64 buffer_id = 2;
+    Anchor position = 3;
+}
+
+message LspExtOpenDocsResponse {
+    optional string web = 1;
+    optional string local = 2;
+}
+
 message LspExtSwitchSourceHeader {
     uint64 project_id = 1;
     uint64 buffer_id = 2;

crates/proto/src/proto.rs

@@ -314,6 +314,8 @@ messages!(
     (UsersResponse, Foreground),
     (LspExtExpandMacro, Background),
     (LspExtExpandMacroResponse, Background),
+    (LspExtOpenDocs, Background),
+    (LspExtOpenDocsResponse, Background),
     (SetRoomParticipantRole, Foreground),
     (BlameBuffer, Foreground),
     (BlameBufferResponse, Foreground),
@@ -464,6 +466,7 @@ request_messages!(
     (UpdateProject, Ack),
     (UpdateWorktree, Ack),
     (LspExtExpandMacro, LspExtExpandMacroResponse),
+    (LspExtOpenDocs, LspExtOpenDocsResponse),
     (SetRoomParticipantRole, Ack),
     (BlameBuffer, BlameBufferResponse),
     (RejoinRemoteProjects, RejoinRemoteProjectsResponse),
@@ -552,6 +555,7 @@ entity_messages!(
     UpdateWorktree,
     UpdateWorktreeSettings,
     LspExtExpandMacro,
+    LspExtOpenDocs,
     AdvertiseContexts,
     OpenContext,
     CreateContext,