Added a testimonial section on the index page

[olivierdalang]

Took some random comments from the google play store, not sure if allowed ?

[mbernasocchi]

@olivierdalang Thanks a lot for this, sorry on the late answer, we're looking for high profile users to add the text to your design.

[mbernasocchi]

@m-kuhn could you add the Deutsche bahn text?

@olivierdalang could we add something like https://www.freshworks.com/freshdesk/lp/home/#customers higher than the testimonials here