Implemented things/request snippets here

These are implemented/fixed here: 
https://github.com/fivethree-team/vscode-svelte-snippets/issues/15
https://github.com/fivethree-team/vscode-svelte-snippets/issues/14
https://github.com/fivethree-team/vscode-svelte-snippets/issues/11
https://github.com/fivethree-team/vscode-svelte-snippets/pull/13
https://github.com/fivethree-team/vscode-svelte-snippets/pull/10