So today I was updating one of our SPFX extensions to use the latest spfx framework (1.16) with node (16.13) and after finishing my updates I got the following inside my code:
I am not exactly sure why these are not coming in, I suspect the newest version of spfx moves these classes out of sp-application-base, but why? and where is the documentation for it? Because there is this link that is only 6 months old and explains to use this code for the top and bottom headers.
I was expecting this code to remain in sp-application-base, but it appears it isn't in that package.