Added info about implemented algorithms

Docs/compression.md

@@ -1,9 +1,15 @@
-ImgBot uses [ImageMagick](http://www.imagemagick.org) to optimize images through the `LosslessCompress()` routine from the The .NET wrapper [Magick.NET](https://github.com/dlemstra/Magick.NET).
+
+**ImgBot** uses compression algorithms to optimize images, and by default `LosslessCompress()` is used.
 This means that while the file size is going down, the quality and dimensions remain intact.
 
-The file size is measured before and after compression and the results are reported in the commit message body.
+When configuring your setup, you can choose between non-aggressive `LosslessCompress()` and aggressive `LossyCompression()` compression.
 
-The images are compressed in place after cloning the repo.
+To provide the strong optimization, **ImgBot** utilizes multiple compression algorithms, and these are currently implemented:
+ - [ImageMagick](http://www.imagemagick.org)
+ - [Svgo](https://github.com/svg/svgo)
+ - [MozJpeg](https://github.com/mozilla/mozjpeg)
+
 
-Once installed into any repo, ImgBot will run the `LosslessCompress()` routine on an ongoing basis and open PRs to keep your images optimized.
+The images are compressed in place after cloning the repo, and once installed into any repo, **ImgBot** will run the `LosslessCompress()` routine on an ongoing basis and open PRs to keep your images optimized.
 
+The file size is measured before and after compression and the results are reported in the commit message body, to keep you updated.