since SPFx 1.21.x we should be using TS v5 -> https://learn.microsoft.com/en-us/sharepoint/dev/spfx/release-1.21#typescript-5x-support

if we look at a newly scaffolded project in SPFx 1.21.x we see that TS v5 only accepts patch version updates and it should stay in v5

We should add validation to the spfx project doctor command for SPFx 1.21.0 and 1.21.1 to check if TS version in the package.json is at least ~5.3.3