chore: sync plugin/marketplace version to 0.12.0 + document the step … #119

Job	Run time
coverage (llvm-cov)	31s
msrv (rust 1.88)	6m 19s
test (ubuntu-latest)	5m 2s
test (macos-latest)	3m 46s
test (windows-latest)	7m 39s
cargo-audit (security advisories)	2m 25s
criterion benches (compile only)	27s
	26m 9s

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