[implemented] Pause option in sychronize dirs?

[ghisler(Author)]

3. Only in dark mode, it was trivial to fix
4. Same as 3, it's not specific to this addition
5. I could not reproduce that at all.

[sirksel]

Mr. Ghisler, just wanted to say thanks so much for the pause feature in synchronize dirs. Works great! I just was syncing a couple 8tb drives tonight by file contents and I had to pause the scan a few times to free up disk transfer bandwidth for another operation. It was great to be able to do that so easily. Thanks again.