Automatic sync in background

[lasuillard]

Implement feature to automatically run sync on background, with configurable ON/OFF switch, target folder, sync interval.

• Automatic sync in background using Chrome Alarm API
• Update settings tab with new configs
• Minor refactoring on some components

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 52.60870% with 109 lines in your changes missing coverage. Please review.

Project coverage is 54.64%. Comparing base (5e767a8) to head (789f146). Report is 1 commits behind head on main.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/lib/sync.ts	3.12%	31 Missing :warning:
src/lib/stores.ts	48.93%	12 Missing and 12 partials :warning:
src/lib/settings.ts	45.16%	16 Missing and 1 partial :warning:
src/service-worker.ts	0.00%	15 Missing and 1 partial :warning:
src/lib/chrome/bookmark.ts	0.00%	6 Missing :warning:
src/manifest.ts	0.00%	5 Missing and 1 partial :warning:
src/lib/raindrop/client.ts	0.00%	5 Missing :warning:
src/components/SecretInput.svelte	83.33%	0 Missing and 2 partials :warning:
src/components/Config.svelte	98.59%	0 Missing and 1 partial :warning:
src/pages/options/Page.svelte	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #71 +/- ## ========================================== - Coverage 60.50% 54.64% -5.87% ========================================== Files 21 22 +1 Lines 438 571 +133 Branches 30 39 +9 ========================================== + Hits 265 312 +47 - Misses 147 220 +73 - Partials 26 39 +13 ``` | [Flag](https://app.codecov.io/gh/lasuillard/raindrop-sync-chrome/pull/71/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yuchan+Lee) | Coverage Δ | | |---|---|---| | [unit](https://app.codecov.io/gh/lasuillard/raindrop-sync-chrome/pull/71/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yuchan+Lee) | `54.64% <52.60%> (-5.87%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yuchan+Lee#carryforward-flags-in-the-pull-request-comment) to find out more.

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[codecov[bot]]

Bundle Report

Changes will increase total bundle size by 12.54kB (3.3%) :arrow_up:. This is within the configured threshold :white_check_mark:

Detailed changes

| Bundle name | Size | Change | | ----------- | ---- | ------ | | raindrop-sync-chrome-esm | 392.29kB | 12.54kB (3.3%) :arrow_up: |