static tests: Commit Check does not check for missing Colon

[crasbe]

Description

As discovered in #21711 (comment) by @fabian18, the Commit Check does not check if the Colon is present after the area specification:

drivers/sx126x add optional CONFIG_SX126X_DEFAULT_SYNC_WORD is accepted as a valid commit message, even though the format should be drivers/sx126x: add optional CONFIG_SX126X_DEFAULT_SYNC_WORD.

Perhaps a simple way to check that would be to find the first whitespace in the commit message and see if there's a Colon in front of it. That would also cover commit messages such as boards/nucleo{32,64,144}: do whatever. It would however cause a false alarm when writing it as boards/nucleo{32, 64, 144}: do whatever, but I think that is acceptable.

[crasbe]

Perhaps it could also check for a DELETEME in the commit title or DO NOT MERGE.