enhance(embed): add ability to pin color mode (#7186)

* enhance(embed): add ability to pin color mode

* fix: Move color mode dropdown to the root section

* auto -> system

* style tweaks

* default to light theme

* try and fix eslint

* fix dropdown styles on other browsers

* rm unnecessary eslintrc change

* more explicit color mode select

* make light explicit

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Co-authored-by: kakkokari-gtyih <67428053+kakkokari-gtyih@users.noreply.github.com>

bskyembed/snippet/embed.ts

@@ -68,6 +68,7 @@ function scan(node = document) {
     if (ref_url.startsWith('http')) {
       searchParams.set('ref_url', encodeURIComponent(ref_url))
     }
+    searchParams.set('colorMode', embed.dataset.blueskyColorMode || 'system')
 
     const iframe = document.createElement('iframe')
     iframe.setAttribute('data-bluesky-id', id)