RFC: Allow data from external sources to be displayed

[RHagendoorn]

In our pipelines we generate a number of lighthouse reports to monitor changes in website performance between two pushes. This data we store in an external database. In order to visualise this data we would like to use the perfanalytics project. To support this, perfanalytics should support the following functionality:

1. Ability to register a project on the left side under where the 'Tags' are located. For the project it should be possible to configure a url where the lighthouse data could be retrieved from.
2. When selecting a project, the lighthouse data should be retrieved from the configured url, and it should display the url routes on the main part of the screen, similar to how the urls are displayed now.
3. On selecting one of the routes, it should show a graph with the retrieved data, with the ability to show additional data when hovering over one of the data points.