doc: Add docs for DbOption

[jonathanc-n]

DbOptions should have docs to explain to users what they are for.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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[jonathanc-n]

A bit confused why this is currently failing with :

test tests::fail_build_test ... ok

failures:

---- version::cleaner::tests::test_cleaner stdout ----

thread 'version::cleaner::tests::test_cleaner' panicked at src\version\cleaner.rs:220:9:
assertion failed: !path_to_local(&option.table_path(gen_1, 0)).unwrap().exists()