Add details to the landing page

[ekatef]

The landing page should give an introduction into the app and draft its' capabilities.

As a first suggestion, we have to communicate the following idea: Better energy planning is needed for better future. Modelling & analysis tools are essential for better planning**, where better future is defined as more sustainable, fair and inclusive.

Particular points which we need to reflect are:

• The modelling results provide a high-level overview of the energy transition implications for different countries of the world assessible for the broad audience
• The app is built on the results of PyPSA-Earth modelling runs
• The outputs have been obtained by a run of the main-stream workflow and are fully reproducible, and anyone can do the same for their particular region of interest
• All the technical details are available for exploration, and the app provides an opportunity to dive into analysis of the present and future of a few power system around the world
• Anyone is absolutely welcome to join us in using and developing this ecosystem

As for particular vizualisation requirements, we can formulate the requirements toward the landing page as follows.

1. The major idea must be eye-catching, and the supporting evidence [the main page?] intuitive to navigate
2. The particular technical points should be clear enough
3. Technical details should be easy to find (scenario definitions and assumptions, in the first place)

The above can be also tailored accounting for the particular framing of a launch of the app