doc: recipes, pager template types and styling

[kbond]

A few documentation follow-ups to #60.

• A Recipes section, working through the same problem three ways: iterating GitHub's issue search with a LazyCollection, making it countable with CallbackCollection, then wrapping it in a custom Collection that overrides count() and take() so the API's own paging is used. Each recipe names what the previous one can't do cheaply. The request counts in it are measured, not guessed.
• A pages() caveat. "Each page is a separate query" was only true for Doctrine - a source that reaches an offset by skipping re-reads everything before each page, so walking 2,000 items in pages of 100 costs 249 reads instead of 20. That's now stated, with a pointer to the recipe that fixes it.
• Pager template variables are documented with Twig's types tag and documentation comments, so the Symfony language tools can offer completion and hover. This needs twig/twig 3.13+, hence the dev constraint - the only non-doc change here.
• A short Tailwind example for styling the pager templates via the classes they emit, plus a pointer to it from the templating section.
• Dropped the Page::hasMorePages() row from the lazy/eager table - it's a table of Collection methods.