Add a link to the online documentation.

Update the README with a link to the current draft of the documentation.
This is temporary, at a later stage the documentation will be directly
included in this repository.

Closes #1

README.md

@@ -18,6 +18,11 @@ Available modules
   but which can also be used directly. This module provides notably a
   *xdistr* function to facilitate creating scatter plots.
 
+Samples
+-------
+A draft documentation with some examples of what the library allows to
+is available on <https://incenp.org/notes/2020/pyplot-examples.html>.
+
 Copying
 -------
 Incenp.plotting is distributed under the terms of the GNU General Public