website: Process pagespeed report

[COil]

Let's try to reach 100%:

Current status :

Desktop: https://pagespeed.web.dev/analysis/https-microsymfony-ovh/tjhljx03pz?form_factor=desktop

Mobile : https://pagespeed.web.dev/analysis/https-microsymfony-ovh/tjhljx03pz?form_factor=mobile

Of course, it can be done in several steps, each commit allowing to raise the score by at least 1% can be merged.

List of fix already applied:

• Added image width and height