Update Electron for Mac fix & esbuild for vuln warning

Esbuild vuln is dev only, and completely irrelevant anyway, but nice to
tidy up.

Mac fix is for Tahoe - a recent Electron fix has just resolved an issue
where all Electron apps creates lag everywhere.

This requires bumping Electron quite a way, which always implies
dropping MacOS Catalina support. Sticking with the latest v37 instead of
v38 to keep Big Sur support for a tiny bit longer.

Author: pimterry