Link to github pages docu from Readme

Author: fangohr

Readme.md

@@ -15,7 +15,7 @@ The book is available as
 - interactively [as Jupyter Notebooks on MyBinder](https://mybinder.org/v2/gh/fangohr/introduction-to-python-for-computational-science-and-engineering/master?filepath=index.ipynb); probably the most attractive version of the book as any code examples can be executed and modified immediately to explore the language and improve one's understanding.
   ([Use JupyterLab](https://mybinder.org/v2/gh/fangohr/introduction-to-python-for-computational-science-and-engineering/master?urlpath=lab/tree/index.ipynb) instead of the traditional Notebook.)
 
-- html ([in this zip file](https://github.com/fangohr/introduction-to-python-for-computational-science-and-engineering/archive/master.zip))
+- html ([in this zip file](https://github.com/fangohr/introduction-to-python-for-computational-science-and-engineering/archive/master.zip) or [here for online browsing](doc/index.html))
 - [pdf](https://github.com/fangohr/introduction-to-python-for-computational-science-and-engineering/raw/master/pdf/Introduction-to-Python-for-Computational-Science-and-Engineering.pdf)
 - downloadable Jupyter Notebook files (`*.ipynb`) ([in this zip file](https://github.com/fangohr/introduction-to-python-for-computational-science-and-engineering/archive/master.zip))