Version 1.1 of package Sed-Mode has just been released in GNU ELPA. You can now find it in M-x list-packages RET.
Sed-Mode describes itself as: ============================== Major mode to edit sed scripts ============================== More at https://elpa.gnu.org/packages/sed-mode.html ## Summary: This major mode provides basic support for Sed scripts. Despite its simplicity, I hope this major mode will be overkill for you. The functionality supported is: - Font-locking ## Recent NEWS: Since V1.0: - Improve the `Commentary'. Version 1.0: Initial release.