Report download size required for the initial render

[adamziel]

Let's create a CI check that measures megabytes required for the initial website paint and the "required offline assets" size. It should be green if the change is less than 50kb and post a comment with an information if a given pr increases that size by more — OR decreases it by more. The comment should contain two sections:

• assets required for the first paint — with total size and a table of 10 largest files, and files with largest delta if we can identify them (build hash may be different than in the previous build)
• assets required for the offline mode — with the same details as above