Summary

1. Dynamically set the HTMLlang attribute based on URL hash. This attribute must be set properly in order to trigger auto-translation features on applicable Chromium-based browsers (Chrome, Edge). Note that this fix works only for the initial page load aslang attribute changes are not recognized on hash change. For example:

   https://docsify.js.org/

   <htmllang="en">

   https://docsify.js.org/#/zh-cn/

   <htmllang="zh-cn">

2. Remove thewrite-a-plugin.md alias as it appears to be unnecessary

3. Add Russian and Spanish search-related label translations

What kind of change does this PR introduce? (check at least one)

• Feature
• Docs

If changing the UI of default theme, please provide thebefore/after screenshot:

• Before (notice the lack of the translation option in the URL bar)
  

• After
  

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g.fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

• Chrome
• Firefox
• Safari
• Edge
• IE