GBCompo21: Add entries section (#54)

* GBCompo21: Add entries section

Includes a link to download all entries as a zip file from the gbcompo21 Github Releases page

* GBCompo21: capitalize github

Author: bbbbbr

website/gbcompo21.md

@@ -49,6 +49,9 @@ Winning entry for the **Music** category: Zilogized
 
 Winning entry for the **Tools** category: Brainfox
 
+## Entries
+The complete set of entries is available to browse on [Itch.io](https://itch.io/jam/gbcompo21/entries) or can be downloaded as a zip file from [GitHub](https://github.com/gbdev/gbcompo21/releases/tag/gbcompo21_entries).
+
 
 ## Sponsors