fix #142: list supported scms

Author: RonnyPfannschmidt

README.rst

@@ -9,6 +9,13 @@ Additionally ``setuptools_scm`` provides setuptools with a list of files that ar
 (i.e. it automatically adds all of the SCM-managed files to the sdist).
 Unwanted files must be excluded by discarding them via ``MANIFEST.in``.
 
+``setuptools_scm`` support the following scm out of the box:
+
+* git
+* mercurial
+
+
+
 .. image:: https://github.com/pypa/setuptools_scm/workflows/python%20tests+artifacts+release/badge.svg
     :target: https://github.com/pypa/setuptools_scm/actions