This is a VSCode extension which provides language support for Snowpack's Astro static site generator.
This extension includes syntax highlighting for Astro syntax, including both JavaScript and HTML parts as well as Astro's custom syntax. It also comes with many snippets to quickly make use of many parts of Astro's API.
This extension is available in the VSCode Marketplace; install it either from there, by searching "Astro" inside VSCode, or by downloading the package found in the releases tab.
Just load an Astro file with a file extension of .astro in VSCode and Astro syntax highlighting should occur.