DOC: added Stack Overflow link to readme file (scipy#21267)

Author: ChVeen

README.rst

@@ -27,7 +27,8 @@ ODE solvers, and more.
 - **Website:** https://scipy.org
 - **Documentation:** https://docs.scipy.org/doc/scipy/
 - **Development version of the documentation:** https://scipy.github.io/devdocs
-- **SciPy development forum:** https://discuss.scientific-python.org/c/contributor/scipy 
+- **SciPy development forum:** https://discuss.scientific-python.org/c/contributor/scipy
+- **Stack Overflow:** https://stackoverflow.com/questions/tagged/scipy
 - **Source code:** https://github.com/scipy/scipy
 - **Contributing:** https://scipy.github.io/devdocs/dev/index.html
 - **Bug reports:** https://github.com/scipy/scipy/issues