Bump version to v1.1.0.

[mtias]

• Add blocks "slash" autocomplete—shortcut to continue adding new block without leaving the keyboard.
• Add ability to remove an image from a gallery from within the block (selecting image).
• Support and bootstrap server-registered block attribute schemas.
• Improve accessibility of add-new-category form.
• Documentation gets an updated design and content improvements.
• Adjust column width calculation in gallery block to properly respect column count.
• Move pending review control together with sticky toggle at the bottom.
• Add caption styling for video block.
• Allow removing a "classic text" block with backspaces.
• Allow Button block to show placeholder text.
• Drop the deprecated button-secondary class name.
• Fix link dialog not showing in Safari when caret is in the middle of the word.
• Fix adding new categories and position newly added term at the top.
• Fix the resetting of drop-zone states after dropping a file.
• Fix embed saving "undefined" text when URL is not set.
• Fix placeholder styling on Text when background color is set.
• Update Composer + PHPCS.
• Rename default block handlers.
• Update code syntax tabs in docutron.
• Link to plugin download and github repo from docutron.
• Added block API document.
• Add "Edit and Save" document.