Improve size threshold warning #1786

Job	Run time
CSS for HTML themes	1m 38s
NodeJS for prerender	1m 36s
PDF/LaTeX backend	7m 32s
Documentation: html	2m 14s
Linkcheck: online tests	1m 31s
Documentation: pdf	3m 44s
Julia 1.6 - ubuntu-latest - x64	5m 57s
Julia 1.6 - macos-latest - x64	7m 7s
Julia 1.6 - windows-latest - x64	13m 19s
Linkcheck: Documenter manual	7m 21s
Julia 1 - ubuntu-latest - x64	5m 12s
Prettier (JS code formatting)	4s
Julia 1 - macos-latest - x64	7m 24s
Julia 1 - windows-latest - x64	7m 58s
Julia nightly - ubuntu-latest - x64	5m 45s
Julia nightly - macos-latest - x64	5m 46s
Julia nightly - windows-latest - x64	7m 3s
Julia 1 - ubuntu-latest - x86	6m 4s
	1h 37m 15s

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