Merge updates to other branch

[TanvirOnGH]

No description provided.

[what-the-diff]

PR Summary

• New Styling for the Sidebery Addon
  A new file was added (addons/sidebery-styles.css) that contains custom styles specifically designed for the Sidebery addon. These enhancements include new variables and animations.

• Enhancements to Toolbar Button Look and Feel
  The chrome/bar/buttons.css file has been updated to bring about a fresh look and animate transitions for various toolbar buttons.

• URL Bar Input Revamp
  The appearance of the URL bar input container has been improved with a revision in the chrome/bar/urlbar.css file.

• Context Menu Visuals Update
  Customized styles have been added to chrome/menu/contextmenu.css improving the the context menu's background and foreground colors.

• Improvements for Rounded Elements Design
  The chrome/misc/round-items.css file now contains new styles for rounded elements such as the URL bar input and main menu, enhancing the overall user interface.

• Updated Documentation
  The readme.md file has been updated to include additional notes and information about the repository, ensuring better understanding.