Enhance src/README.md especially about Git/GitHub workflow.
Enhance src/README.md especially about Git/GitHub workflow.

We should define a bit more 'minimal' rules.
But the project is in a very early stage,
so perfect rule is not necessary.

NobuoK/xyzzy,NobuoK/xyzzy,NobuoK/xyzzy,NobuoK/xyzzy,NobuoK/xyzzy