Release v1.2.0

• Support prefix // (double slash) to search rustc crates docs. 👉 Learn more.
• Support search released Rust versions quickly. 👉 Learn more.
• Add source code mode (with src: or with alias s:) to open the source code page directly. 👉 Learn more.
• New commands:
  • :blog: show all Rust release blog posts.
• Improvements:
  • Add a reminder for Firefox offline mode on the popup page. Fix #94.
  • Add fallback search strategy for @crate search. Fix #96.
  • Only open update page once a day if the auto-update is on. Fix #97.
  • Add more useful tips for the :help command.
  • Compress history's JSON data slightly.
• Bugfix:
  • Fix the compatibility for the new style of search-index.js format. Fix #106.
  • Fix the compatibility of search-index.js on-demand load mode. See this commit eefa192c.
  • Add validation when auto index std search-index. Fix #99.
  • Fix compatibility issue of the new const-since link in Rust docs page.
  • Fix search statistics bug for https://docs.rs/releases data.