Add Readme file to docs folder.

Author: ajdavidl

docs/Readme.md

@@ -0,0 +1,31 @@
+## Sphinx documentation
+
+It uses the [sphinx](https://www.sphinx-doc.org/en/master/) package.
+
+### Requirements:
+
+It's necessary to install two additional packages:
+
+```bash
+pip install sphinx-rtd-theme
+pip install sphinx-markdown-builder
+```
+
+### Update `rst` files:
+
+```bash
+sphinx-apidoc -o . ..
+```
+
+### Create documentation
+
+In html:
+
+```bash
+make html
+```
+In markdown
+
+```bash
+make markdown
+```