Bump version number to 5.6.0-rc.1

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Changelog

Enhancements

• Improve focus state for button block.
• Reduce specificity of block styles to make it easier for themes to style the editor.
• Optimize data subscribers to avoid unnecessary work on each editor change.
• Avoid overlapping block breadcrumb when block movers are visible for full- and wide-aligned blocks.
• Preload user permissions for reusable blocks to avoid UI flickering for block settings menu options.
• Remove unnecessary bottom padding for nested lists.
• Restore block movers to focus mode.
• Improve display of categories list panel.

Bug Fixes

• Restore block movers to full- and wide-aligned blocks.
• Always show drag handles for nested blocks, even when only a single block exists.
• Improve HTML output for formatted text.
• Fix an error preventing registerFormatType to be called wrongly indicated as duplicate.
• Resolve problematic post lock release behavior when leaving the editor when using newer versions of Chrome.
• Resolve an issue to detect autosave presence at editor load in considering saveability.
• Resolve a typo which could interfere with audio shortcode transforms.
• Apply RichText attributes correctly to resolve an issue with registerFormatType.
• Preserve attributes of a multi-line classic block paragraph.
• Resolve an issue for Windows and Linux development mode due to a access key safeguard.

Various

• Refactor a number of core blocks toward better interoperability with the Blocks RFC: [1], [2], [3], [4].
• Move selection state for RichText components to the block editor store, to enable future work to resolve or improve selection behavior.
• Change the behavior of reusable blocks autocomplete to fetch upon input, improving reliability of tests and avoiding unnecessary network requests.
• Allow development mode constant to be redefined by plugins.
• Improve reliability of e2e tests: [1], [2], [3].
• Avoid running files contained in the git subfolder as tests.
• Resolve an issue with e2e errors related to dependencies updates.
• Add a new ESLint rule to enforce accessible use of BaseControl.
• Remove redundant CSS styles.
• Add e2e tests for dynamic allowed blocks, transforms from media to embed block, [explicit persistence undo regression](Testing: Add Undo test for explicit persistence undo regression #15049.
• Add a new wpDataSelect e2e test utility.
• Include a React hooks ESLint configuration.
• Add a new Webpack plugin to help externalize and extract script dependencies (not yet published).

Documentation

• Include auto-generated documentation for core data module actions and selectors.
• Update contributing documentation to extract detailed sections to their own documents.
• Document the withGlobalEvents higher-order component creator.
• Add related resources for BlockEditor components.
• Clarify requirements for e2e-test-utils package.
• Exclude private, experimental, and unstable APIs from auto-generated data documentation.
• Include missing DropZone component props in documentation.
• Mention component stylesheets in usage instructions.
• Update copy/paste support list to reflect paste support of images from Microsoft Word and Libre/Open Office.
• Add [missing "Code is Poetry" footers](Add footers "Code is Poetry" are missing #15140.
• Improve wording of JavaScript Tutorial document.
• Improve Travis build performance by expanding containers for e2e tests.

Mobile

• Refine transitions for bottom sheets.
• Extract a HorizontalRule component for use in a cross-platform separator block.
• Fix an error with changing list types.
• Avoid setting caret when rich-text text will be trimmed.
• Fix title not focusing.
• Improve post title accessibility.
• Improve image block accessibility for deselected, and selected states.
• Add accessibility label for unselected paragraph.
• Fix history stack when not empty on a fresh start of the editor.
• Improve Heading block accessibility.
• Make accessibility string properly localizable.
• Update string concatenation for accessibility labels.