docs: Add instructions on how to self-sign bitcoin-core binaries for macOS

Remove link and clear up language

Move instructions to release-notes-empty-template.md

Capitalize 'Bitcoin Core' project name

Author: Christewart

doc/release-notes-empty-template.md

@@ -32,6 +32,13 @@ Upgrading directly from a version of Bitcoin Core that has reached its EOL is
 possible, but it might take some time if the data directory needs to be migrated. Old
 wallet versions of Bitcoin Core are generally supported.
 
+Running Bitcoin Core binaries on macOS requires self signing.
+```
+cd /path/to/bitcoin-core/bin
+xattr -d com.apple.quarantine bitcoin-cli bitcoin-qt bitcoin-tx bitcoin-util bitcoin-wallet bitcoind test_bitcoin
+codesign -s - bitcoin-cli bitcoin-qt bitcoin-tx bitcoin-util bitcoin-wallet bitcoind test_bitcoin
+```
+
 Compatibility
 ==============