Rename repo to `airnode-docs`

[wkande]

@dcroote Someone (maybe you) brought this up. Renaming the repo is easy but it might be nice to change the project name in Firebase as well. Then I am not sure about the impact to the Firebase previews. What do you think about this issue?

[wkande]

@dcroote Looks like @Siegrift also wants to do this rename, see Slack here

We could do this and upgrade the VitePress version at the same time.

[dcroote]

I'm happy to rename it in GitHub, but the .firebaserc file has to remain as is:

https://github.com/api3dao/vitepress-docs/blob/bf5e0305497f962dbfa759ecbcef14f5bb35c07f/.firebaserc#L1-L5

because in Firebase you cannot rename the project ID, and it is set as:

[dcroote]

Renamed