Improve Shredder attachments regex

[federicobaldo]

In order to match also _ and - characters.

[sunnavy]

thanks for the commit.

"-" part looks good to me.

note that "\w" already matches "_", so it's not necessary to explicitly add "_".

[federicobaldo]

Thanks, applied your suggestion.

[sunnavy]

To make the merge more clear, maybe you can combine the 2 commits instead? thanks!

[federicobaldo]

Done, cheers!