[feat] Block comment for extra (such as append)

[ilan-schemoul]

Hello,
At work I need block comments for everything including one line comment.
I'd love to be able to either force block comments for everything or have an option to add mappings for extra (append, newlines etc.) for block comments

[ilan-schemoul]

I realized what I really (really) need is an option ton always use block comments. Because my job forbids me to use non inline comments (coding rules).
I made this PR #478