Renaming default branch from "master" to "main"

[Zdenko Podobny]

Hi all,

Just a friendly warning: If you are for whatever reason using the latest code from git, be aware that there was the name change of the default branch from "master" to "main". 

Some details are on https://github.com/tesseract-ocr/tesseract/issues/3554

Please adjust your projects/workflow accordingly.

Sorry for any inconvenience and problems.

Kind regards,

Zdenko