compress html blobs sent from GitLab.com to browser

Description

Per https://gitlab.com/gitlab-org/gitlab-ce/issues/33501,

"Obviously the smaller the resources, the faster they will arrive in the browser. Currently we're not compressing HTML responses. Even with low gzip compression levels, we could be speeding up page loads, particularly on slow connections."

Proposal

• Investigate if it makes sense to compress HTML responses, and if yes: do it.

Links / references

Documentation blurb

(Write the start of the documentation of this feature here, include:

1. Why should someone use it; what's the underlying problem.
2. What is the solution.
3. How does someone use this

During implementation, this can then be copied and used as a starter for the documentation.)