b527d364dc
This commit reinstates the single-page variant for the Spring Boot reference documentation. Now the single and multi-page variants are hosted under the same `"html"` folder, as `"index.html"` and `"single-index.html"`. Note that files ending in `"index.html`" are treated as index files by the spring-doc-resources project and their table of contents do not display a "Back to index" link. Fixes gh-16295