Closes #94 Closes svelte-add/svelte-add#193 Closes svelte-add/svelte-add#507

This is a pretty rough poc to try and make sv work better with .svelte files. Under the hood, this uses svelte-ast-print

Step 1 (support for svelte files):

• support for svelte specifc html syntax (@attach, self closing component tags, transitions, etc)
• check and adapt all other usages of parseSvelte
• make svelte-ast-print support indentation and quote styles (I think some of that already works)
• fix formatting mistakes in svelte-ast-print (first write up: xeho91/js-ast#128)

Step 2 (reduce deps, different pr probably)

• we currently use many different libraries for parsing and serializing JS / CSS / HTML. All of that could in theory be handled by svelte/compiler and svelte-ast-print. Check which hoops we need to jump to make that happen. We could potentially drop the following deps:
  • dom-serializer
  • domhandler
  • domutils
  • htmlparser2
  • postcss