Svelte: Change file extension to .svelte

[Rich-Harris]

The people have spoken — we should use the .svelte file extension for Svelte components.

• [x] update tests
• [x] update Sapper to recognise .svelte files OOTB
• [x] update rollup-plugin-svelte, svelte-loader etc rollup-plugin-svelte already supports it, svelte-loader doesn't know about extensions (that goes in the webpack config itself)
• [x] update sveltejs/template, sveltejs/template-webpack, sveltejs/sapper-template
• [x] update docs (including adding instructions for adding the VSCode extension, or for associating .svelte with HTML)
• [ ] create extensions for Sublime etc?
• [x] update REPL
• [x] TextMate grammar (this could be a good starting point, though it's Svelte 2 and will need some tweaks)
• [ ] probably a bunch of other stuff

[scorsi]

Just to say that Svelte isn't recognised yet by GitHub as a language, but someone did a PR to the GitHub's Linguist repository (I wanted to do it before I saw someone already did it) to add the Svelte support, here: https://github.com/github/linguist/pull/4504. So it may be supported in some times in Github, hourra ! 🎉

[antony]

A quick look through the docs tells me that the conversion from .html to .svelte is complete, and the PR has been merged into linguist :tada: and the remaining items here are:

[ ] Add instructions for IDE setup / sublime / intellij (there is an open PR for some of this, but I think it needs a PR/issue of its own if somebody is willing to do this for each IDE)
[ ] A bunch of other stuff which really isn't actionable.

On this basis I think it's safe to close this stale issue and let these issues come out of the woodwork on their own.