EPIC: Fast PWA

[andreslucena]

Is your feature request related to a problem? Please describe.
Loading Decidim is pretty slow most of the time. This is specially important as there are metrics (and experiences) that shows that participants wants to have speed:

53% of visits are abandoned if a mobile site takes longer than 3 seconds to load.
March 2016, Google

Describe the solution you'd like

Google Chrome has the Lighthouse tool that gives metrics to some kind of improvements that are important to participants. Ideally, we would have green values on every one of these:

Metric name	Time	URL
First Contentful Paint	< 2 seconds	https://web.dev/first-contentful-paint
Speed Index	< 4 seconds	https://web.dev/speed-index
Time to Interactive	< 5 seconds	https://web.dev/interactive
Largest Contentful Paint	< 2.5 seconds	https://web.dev/lighthouse-largest-contentful-paint/

Additional context

Lighthouse relevant section

Lighthouse relevant section

As some of these changes could be particular for a given provider (i.e. it's not the same Heroku/AWS/OVH/Digital Ocean), at the beginning of these developments there should be done some Performance and reproducible testing, and it should also be on someway integrated on the Continuous Integration platform being use at the moment of development, so we have a comparison point (an initial picture) and also detect regressions. As the other issues in this EPIC will handle all the performance improvements, and this is only about having the monitoring in place, we will have a timeout of 10 seconds or something like that, with the purpose of making the test always pass. Then in every of the

Does this issue could impact on users private data?
No, it's about performance.

Related issues

• Configure time monitoring metrics at CI - Configure time monitoring metrics at CI #8470
• First Contentful Paint - Optimize First Contentful Paint #8471
• Speed Index - Optimize Speed Index #8472
• Time to Interactive - Optimize Time to Interactive #8473
• Largest Contentful Paint - Optimize Largest Contentful Paint #8474