Sharpmake's project new default branch: main

[jspelletier]

Hi Sharpmake!

As of today, the default branch for Sharpmake Git project is main (was previously dev).

The dev branch will be deleted in the following days.

This move aims at simplifying the Git repository and its release process.

If you have some branches based on dev, nothing is expected to happen: when you will create a pull request, Github will automatically select the current default branch (main) as target.

If you have some local commits on dev, you will (as before) need to create a new branch to push them on github(and then create a pull request).

If you have a fork, you can continue to work as you wish. It doesn't impact future merge requests targeting the upstream project.

All existing opened pull requests have been edited to use the main branch as target.

Thanks