Update ansi theme to highlight JSON keys separately from string values

CHANGELOG.md

@@ -64,6 +64,7 @@
 - Updated Catppuccin, see #3333 (@SchweGELBin)
 - Updated gruvbox, see #3372 (@Nicholas42)
 - Updated GitHub theme, see #3382 (@CosmicHorrorDev)
+- Updated ANSI theme to highlight JSON object keys differently from values, see #3413 (@keith-hall)
 
 ## `bat` as a library
 

assets/themes/ansi.tmTheme

@@ -234,7 +234,7 @@
                 <key>name</key>
                 <string>Headings</string>
                 <key>scope</key>
-                <string>markup.heading punctuation.definition.heading, entity.name.section, markup.heading - text.html.markdown</string>
+                <string>markup.heading punctuation.definition.heading, entity.name.section, markup.heading - text.html.markdown, meta.mapping.key string.quoted.double</string>
                 <key>settings</key>
                 <dict>
                     <key>fontStyle</key>