[fidlbolt] highlight open, closed, ajar

Update the syntax highlighting to support the new unknown interaction
modifiers (open, closed, ajar).

Note that this will highlight any use of thiese modifiers (e.g. a struct
field named open), unlike the vscode syntax which only applies these
modifiers to protocols.

Bug: 88366
Test: ran fidlbolt locally and checked highlighting
Change-Id: I6cadb6814dadbb279ef9a5caa71164682172afa0
Reviewed-on: https://fuchsia-review.googlesource.com/c/fidlbolt/+/760147
Reviewed-by: Mitchell Kember <mkember@google.com>
diff --git a/frontend/src/ace-modes.js b/frontend/src/ace-modes.js
index b72d1d9..0486b64 100644
--- a/frontend/src/ace-modes.js
+++ b/frontend/src/ace-modes.js
@@ -138,7 +138,7 @@
           },
           {
             token: 'keyword',
-            regex: /\b(?:alias|as|bits|box|compose|const|enum|flexible|library|optional|protocol|reserved|resource|service|strict|struct|table|type|union|using)\b/,
+            regex: /\b(?:ajar|alias|as|bits|box|closed|compose|const|enum|flexible|library|open|optional|protocol|reserved|resource|service|strict|struct|table|type|union|using)\b/,
           },
           {
             token: 'support.type',