feat: adds .hbs HTML language extension

[willviles]

Thanks for the great extension! This PR adds hbs as a valid HTML language extension, most commonly used by Ember.js developers using Tailwind in HTMLBars templates.

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For use before this PR is merged and released:

npm install -g vsce
git clone -b feat/add-hbs-html-language git@github.willviles/vscode-tailwindcss.git
cd vscode-tailwindcss
npm install
vsce package

Then install the generated .vsix file by running the VSCode command 'Extensions: Install from VSIX...'

[Alonski]

@bradlc Can we get this merged and released please?

[bradlc]

Thanks for the pull request @willviles! Unfortunately I did a major rewrite of the extension and wasn't able to merge this, but hbs is now one of the languages with built-in support 🎉