Add completions for :global(...) modifier in styles

[AleksandrSl]

<style> blocks in components can have :global(...) modifier (https://svelte.dev/docs#style). At the moment css completion doesn't take these styles into account.

Related to #60 and #70

[tomblachut]

Also relevant:

If you want to make @keyframes that are accessible globally, you need to prepend your keyframe names with -global-.

The -global- part will be removed when compiled, and the keyframe then be referenced using just my-animation-name elsewhere in your code.

[tomblachut]

Moved to WEB-62307 Svelte: add completions for :global(...) modifier in styles