mutt: Fix dev docs to use head without SHA1

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>
mutt: Add confirm-attachment patch

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>
mutt: Fix slang - should be s-lang

Closes #20893.

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>
mutt: fix second 'slang' usage