feat: A draft for the about page in Elk [MOSOWEB-54]

[bakulf]

This PR contains a draft for the about page in Elk. It works as expected but I think it needs a bit of love with the style (vue, css are not my thing (yet?)).

A few considerations:

• I don't know if you have templates for PRs.
• in theory, we don't need the server-side call to fetch the extended_description endpoint, but I see this as a common pattern elsewhere (invite page)
• to push to prod, we need to change the HAProxy, adding use_backend elk if { path_beg /about }

[jpezninjo]

I think the server-side call pattern is just a way to have consistent language between web and mobile. Totally can go away imo

[jpezninjo]

Just the one small comment about the email. The page looks great already to me :D

[bakulf]

I added the authorization header for the instance API endpoint.
We need to revisit how we want to interact with mastodon >=4.2.1

[bakulf]

I added the authorization header for the instance API endpoint. We need to revisit how we want to interact with mastodon >=4.2.1

OK. It seems a wrong config for stage. We are good to go.