Add link to gulp-rev-dist-clean in the readme

[alexandre-abrioux]

Hi! First of all thank you for maintaining this package! I used it quite a lot in the past and loved it :)

I created gulp-rev-dist-clean back in 2017 out of a need I had to clean-up old files that had been removed from the src directory but that where still present in the dist directory even after running gulp-rev.

Usually you would completely empty the dist directory before running gulp-rev, so that everything in the dist directory would correspond to actual files in the src directory, but this could get heavy with huge builds in watch mode. To prevent re-building everything, especially images, each time a file changes, and to keep the dist directory "fresh", I needed a solution.

I tried other packages at that time, including rev-del, but it did not support this specific use-case, so I decided to develop my own.

Fast forward to today, I am still maintaining it and adding new features to it as it turns out it is also used by others. Therefore I wonder if we could add it to the list of "clean-up" tools offered by the community?

Thanks!