Discussion sign and diagnostics (#78)

This MR adds support for in-line comments in the review pane. This allows you to view comments (as diagnostics) directly in the Neovim buffers that you are reviewing. You can then jump to them directly in the discussion tree if you want to reply, edit, and so forth.

lua/gitlab/state.lua

@@ -33,6 +33,36 @@ M.settings = {
     resolved = "✓",
     unresolved = "",
   },
+  discussion_sign_and_diagnostic = {
+    skip_resolved_discussion = false,
+    skip_old_revision_discussion = false,
+  },
+  discussion_sign = {
+    -- See :h sign_define for details about sign configuration.
+    enabled = true,
+    text = "💬",
+    linehl = nil,
+    texthl = nil,
+    culhl = nil,
+    numhl = nil,
+    priority = 20,
+    helper_signs = {
+      -- For multiline comments the helper signs are used to indicate the whole context
+      -- Priority of helper signs is lower than the main sign (-1).
+      enabled = true,
+      start = "↑",
+      mid = "|",
+      ["end"] = "↓",
+    },
+  },
+  discussion_diagnostic = {
+    -- If you want to customize diagnostics for discussions you can make special config
+    -- for namespace `gitlab_discussion`. See :h vim.diagnostic.config
+    enabled = true,
+    severity = vim.diagnostic.severity.INFO,
+    code = nil, -- see :h diagnostic-structure
+    display_opts = {}, -- this is dirrectly used as opts in vim.diagnostic.set, see :h vim.diagnostic.config.
+  },
   pipeline = {
     created = "",
     pending = "",