Improve Lighthouse Score to 90 in all categories

[jaronheard]

From our Front-End Charter, one of our tactical goals is to improve performance, as measured by our Lighthouse score. We've targeted a score of above 90 in all categories.

Why:

Poor performance can, and does, lead to exclusion. This point is extremely well documented by now, but warrants repeating. Sites that use an excess of resources, whether on the network or on the device, don’t just cause slow experiences, but can leave entire groups of people out. - https://timkadlec.com/remembers/2019-01-09-the-ethics-of-performance/

How:

1. Measure current state

• Saved lighthouse scores from the beginning of the season here.

2. Implement continuous measurement of current state

• Implement lighthousebot on ci Implement lighthousebot on Travis for PRs #563

3. Make improvements to performance

• Make changes that improve performance, and repeat until the objective is met
  This ~15 minute video gives an overview of the basics of how to use Lighthouse to identify performance issues and measure changes, but you can go deep on web performance.