Add Plausible to v1

[vgeorge]

Contributes to #151.

Changes:

• Add Plausible domain to config/base.js
• Update gulpfile to inject domain into index.html on build
• Update Github Actions to disable staging build as we only have one deployed environment for v1

cc @aboydnw

[vgeorge]

@geohacker it looks like our Azure deploy keys for the production environment have expired, would you be able to update them? We need to update AZURE_CREDENTIALS_PRODUCTION secret.

[aboydnw]

@vgeorge thanks for starting this. @geohacker It would be awesome to have this running by the end of this week, to be included in the product team's metrics for our quarterly goal next week, if you have time to get to it