pkp/pkp-lib#13242 Add new Blade theme Eidos - #5784

This commit has been squashed to remove the code churn that occurred
through different refactors. The following commit messages record
what has been squashed:
- Add: homepage block with recent issues swiper
- Add: homepage block with a search prompt
- Add: homepage block for latest publications by category
- Reorganise blade template files
- Refactor: remove Layout component
- Refactor: use new helper function to get primary/supplementary galleys in ArticleHandler
- Refactor: pass galley genre ids from source
- Move issue templates around based on which have eidos theme requirements
- Fix: heading levels in issue summary
- Fix: adjustments for RTL languages
- Fix: remove typo
- Add: option to show article galleys or cover image in issue toc
- Fix: wrong URL to latest articles on site homepage
- Fix: add missing homepage block registration
- Add: browse by category homepage block
- Remove unused code in latest articles homepage block
- Switch to locale key in ojs app
- Add: latest articles homepage block
- Fix: copypasta typo in code comment
- Fix: make homepage blocks available at site-wide index page
- Refactor: load metadata blocks in ArticleHandler
- Rewrite frontend comments components for Eidos theme
- Refactor: add typed helper method for displaying system message templates
- Refactor: replace error and message templates with one system-message template
- Add: pass site to all templates
- Add: id to each publication ID for a journal
- Add issue table of contents homepage block
- Add: homepage blocks registry
- Initial work on article metadata blocks
- Add: useful template variable name in article page for cross-app consistency
- Add: default metadata blocks
- Fix: wrong prop on example metadata block in HtmlArticleGalleyPlugin
- Add: example custom plugin metadata block in HtmlArticleGalleyPlugin
- Add: OJS-specific Layout component for Blade themes
- Fix: Blade errors when template variables are undefined