docs: Validate JSON snippets (settings, keymap, tasks, etc) (#40043)

Closes #ISSUE

Release Notes:

- N/A *or* Added/Fixed/Improved ...

docs/src/diagnostics.md

@@ -8,7 +8,7 @@ By default, Zed displays all diagnostics as underlined text in the editor and th
 
 Editor diagnostics could be filtered with the
 
-```json5
+```json [settings]
 "diagnostics_max_severity": null
 ```
 
@@ -16,7 +16,7 @@ editor setting (possible values: `"off"`, `"error"`, `"warning"`, `"info"`, `"hi
 
 The scrollbar ones are configured with the
 
-```json5
+```json [settings]
 "scrollbar": {
   "diagnostics": "all",
 }
@@ -32,7 +32,7 @@ Or, `editor::GoToDiagnostic` and `editor::GoToPreviousDiagnostic` could be used
 Zed supports showing diagnostic as lens to the right of the code.
 This is disabled by default, but can either be temporarily turned on (or off) using the editor menu, or permanently, using the
 
-```json5
+```json [settings]
 "diagnostics": {
   "inline": {
     "enabled": true,
@@ -49,7 +49,7 @@ Project panel can have its entries coloured based on the severity of the diagnos
 
 To configure, use
 
-```json5
+```json [settings]
 "project_panel": {
   "show_diagnostics": "all",
 }
@@ -61,7 +61,7 @@ configuration (possible values: `"off"`, `"errors"`, `"all"` (default))
 
 Similar to the project panel, editor tabs can be colorized with the
 
-```json5
+```json [settings]
 "tabs": {
   "show_diagnostics": "off",
 }