Updated Getting started (asciidoc)
Remove dead link to deleted [Spring support](https://github.com/lettuce-io/lettuce-core/commit/a91d73d161c6beaaee9cbda914fbed5ab93ea5d6). Recommended way is Spring Data Redis.
gradle configuration 'compile' is obsolete and has been replaced with 'implementation' and 'api'. And the keyword has been removed since gradle 7.0.
Updated Getting started (markdown => asciidoc)
Updated Getting started (asciidoc => markdown)
Convert to Asciidoc