add tip to docs for how to find list of supported source languages for the...

add tip to docs for how to find list of supported source languages for the various syntax highlighters

docs/CHANGELOG.adoc

@@ -6,6 +6,9 @@ https://github.com/asciidoctor/asciidoc-docs/commits/main[commit history].
 
 == Published Q1 2023
 
+Added::
+* Add tip for how to find list of supported source languages for the various syntax highlighters
+
 Changed::
 * Clarify that superscript and subscript formatting is neither constrained nor unconstrained, but rather a specialty hybrid
 * Clarify that first menu item must start with word character or character reference

docs/modules/verbatim/pages/source-highlighter.adoc

@@ -73,8 +73,14 @@ In other words, the `source-highlighter` attribute means "`use this syntax highl
 To apply highlighting to a block of source code, you must specify a source language.
 If the block is a literal block or paragraph, you must also specify the `source` style.
 
-The available source language values are defined by the syntax highlighter library.
-In most cases, the source language value is the proper name of the language in lowercase (e.g., `ruby`, `java`).
+The AsciiDoc language does not specify the list of valid source language values.
+Instead, the available source language values are defined by the syntax highlighter library.
+
+TIP: You can find the list of available languages supported by Rouge in the https://github.com/rouge-ruby/rouge/blob/master/docs/Languages.md[Rouge documentation].
+You can print a list of available languages supported by Pygments by running `pygmentize -L formatters`.
+The available languages supported by highlight.js depends on which bundle of highlight.js you are using.
+
+Typically, the source language value is the proper name of the language in lowercase (e.g., `ruby`, `java`).
 Most syntax highlighters also accept using the source file extension (e.g., `js`, `rb`), though it's important to be consistent.
 If the syntax highlighter doesn't recognize or support the source language, the block will not be highlighted.