New perf metric: Web bloat score

#### Description of audit and audit category

Basically, it's the `(total bytes of the webpage) / (bytes of a screenshot of that webpage)`. It's defined at https://www.webbloatscore.com/.

#### Explanation of how it’s different from other audits

No other metrics attempt to judge the efficiency of the bytes used.

#### What % of developers/pages will this impact (estimates OK, data points preferred)

It's a perf metric.. so nearly 100%.

#### How would the audit appear in the report?

Another perf metric. Maybe like this?

#### How is the new audit making a better web for end users? (data points preferred)

The weight of a screenshot of the page isn't typically considered, but serves as a nice reference point that everyone can appreciate. This metric is a lot easier to explain than our other perf metrics. And it addresses a unique measurement that isn't covered by any existing metrics.

#### What is the resourcing situation (who will create the audits, maintain the audits, and write/maintain the documentation)

We're interested in someone contributing this audit. We can help guide them. Once implemented, Lighthouse core team will maintain.

#### Do you envision this audit in the Lighthouse report or the full config in the CLI? If in the report, which section?

🤔 This is a weird question, Lighthouse.

#### How much support is needed from the Lighthouse team?

A bushelful.

#### Any other links or documentation that we should check out?

Nah just https://www.webbloatscore.com/