Please create 19.3 branch

[todi1856]

It seems latest master commit makes this branch only compatible with Unity 2020 and up. Thus trying to open this project with Unity 2019 LTS will throw bunch of errors, since Unity projects are not backwards compatbile

Even though ReadMe says, current Unity version is 2019.3.

Please:

• Update ReadMe stating that current Unity version is 2020 (NOT 2019)
• Please create a branch 19.3 from this commit 91f74c0 where the project was still compatible with Unity 2019.

Thanks!