Switch to 'foreign' behavior for automake invokation

[Romain Bouvier]

Hello,

Now that we have switched to gitlab, we want to have nice README in our projects, as they are more visibles ! :)
Gitlab support markdown, and we need to rename README to README.md to use it. See this beautiful README: https://gitlab.xfce.org/xfce/xfce4-dev-tools/-/blob/master/README.md

automake default to "gnu" behavior, which requires a file named "README": https://autotools.io/automake/options.html

I propose to switch to "foreign" behavior, which is the recommended way, and don't seems to break anything (lots of project use foreign mode).

You can take a look at this commit https://gitlab.xfce.org/xfce/xfce4-dev-tools/-/commit/fa58240b6b0070a6a7e446fa7bd6034eac452542 on xfce4-dev-tools if you rename your README and want to fix your build (add foreign in AM_INIT_AUTOMAKE, and add README.md to dist tarball).


Romain,