Snippet refactor for #9

[octref]

Sorry somehow this slipped off my todo-list 😅

Changes:

• Split snippets into multiple files, corresponding to the README list. They are in the same order now so easier to maintain.
• vue snippet only has vbase, which is available outside <template>, <script> and <style>
• Snippets in vue-template.json are available for both Vue files (only in <template> section) and html files.
• Snippets in vue-script.json and vue-script-vuex.json are availble for both Vue files (only in <script> section) and js files.
• vinc and vdec seems to be for js instead of plaintext, so I moved them to the correct place in Readme.

[artiescie]

Works better, I guess the dependency (vetur) made a change that causes this issue in the snippets since it was clearly working at one point.

I would suggest one more "", in the vbase snippet... to add a newline after the closing <style> tag. That makes the stricter ESLint (rule eol-last) happy that the file ends with a newline.

[sdras]

Thanks for the PR, it's too bad vetur is causing this issue, but I should be able to take a look sometime after this weekend.

[sdras]

Finally had a day off from speaking! Thanks for the PR.