Merge bitcoindevkit/bdk#2171: Add `SECURITY.md` #44

Job	Run time
prepare	4s
Rust fmt	25s
Check WASM	9m 15s
Check documentation errors	1m 20s
Build & Test (1.94.1, --all-features)	3m 54s
Check no_std	39s
Rust clippy	1m 32s
Build & Test (1.94.1, --no-default-features --features bdk_chain/hashbrown)	2m 19s
Build & Test (1.85.0, --all-features)	4m 7s
Build & Test (1.85.0, --no-default-features --features bdk_chain/hashbrown)	2m 41s
Build & Test Examples (example_cli)	39s
Build & Test Examples (example_bitcoind_rpc_polling)	42s
Build & Test Examples (example_electrum)	53s
Build & Test Examples (example_esplora)	59s
	29m 29s

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