From this discussion :

https://elixirforum.com/t/script-tags-in-heex-and-app-js/

Build the extension, including the parser :

npm i
cd parser
npm i
# if needed, depending on your system
npm i -g node-gyp nan tree-sitter-cli
tree-sitter generate
node-gyp configure
node-gyp build
cd ..
npm run compile