tools: add a rudimentary make-a-release script

To make mistake less likely. This is very much untested and subject to
change. We will find out how well this works in next picom release.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

.gitignore

@@ -48,6 +48,7 @@ target
 # Python
 *.pyc
 *.py
+!/tools/*.py
 !/tests/testcases/*.py
 
 # Misc files