The extension is available on both vsce, and on ovsx.
This VSCode extension is a fork of the GitHub project sublime_autotools. It
includes syntax highlighting for Autoconf M4 (.m4, configure.ac...) and
Automake files (e.g., Makefile.am). This extension uses the vscode's own
Makefile syntax support for hghlighting makefile things in automake files. I
chose to fork the sublime project in order to have an easy
way of updating vscode_autotools (which is only a matter of git merge).
Note that the sublime fork also has a Makefile2 (an alternate grammar file for Makefiles) but the standard vscode's Makefile support works much better (actually, the sublime's one is kind of buggy).
The changes to vscode_autotools are documented in CHANGELOG.md.
See DEVELOPMENT.md for more information on how to debug and improve
vscode_autotools.
Note: For Autoconf M4 macros, the arguments may need to be highlighted in several different ways; some are shell code, some are plain text, and a few are C code. There are definitions for the builtin ones, but custom macros may not be highlighted correctly.