Add ability to toggle recommendations on/off

[samturrell]

Feature request summary
It would be good to be able to toggle recommendations on/off in a lighthouse report and see how it affects the scores. For example if there are recommendations for enabling http2, it would be good to see the impact of this, and if it is enough to increase the overall page score when advising on improvements.

Obviously in an ideal world, all recommendations should be followed and implemented, but sometimes we only have resource to improve certain things, or the project is built in such a way where some items are hard/impossible to change.

What is the motivation or use case for changing this?
As above, and we would be able to quickly see the potential impact of future changes.

Given an example of a client using a firewall with their static website, but the firewall isn't set up to use http2, we would give them the recommendation backed up with evidence that this should be updated to increase the scores by X amount.

How is this beneficial to Lighthouse?
It would allow give users insight into the outcome of potential changes

[connorjclark]

Opportunities do not impact the score. The score is based only on the observed metrics (or on a simulation of what the metrics may have been on a slower device). Everything else is just advice.

See https://developer.chrome.com/docs/lighthouse/performance/performance-scoring/

In general the larger the estimated savings of an opportunity audit (the higher it is in the list), the more impact it has on the metrics, but it's just an educated guess.

If you want to estimate how the LH score will change given a known starting metrics and estimated savings, you can use the LH score calculator.