Merge torrust#1359: Add link to packages docs in the README

99a3724 docs: add link to packages docs in the README (Jose Celano)

Pull request description:

  Add link to packages docs in the README.

ACKs for top commit:
  josecelano:
    ACK 99a3724

Tree-SHA512: 1f2c852ce9728e8a2589383948cf07dd6a0bb2ab7ce589772c297c7e37646b416ac7c2199cfd219f3b9774ab553d43baaa870e0207ff298bc56ac4077bab1da8

Author: josecelano

README.md

@@ -69,6 +69,8 @@ Others:
 
 ![Torrust Tracker Layers with main packages](./docs/media/packages/torrust-tracker-layers-with-packages.png)
 
+There is also extra [documentation about the packages](./docs/packages.md).
+
 ## Getting Started
 
 ### Container Version