Catch any standard numbers which do not actually exist

[mpadge]

@helske in https://github.com/helske/bssm/issues/30 reported compliance with "BS7.7" which does not actually exist. This was not caught and should have been.

[mpadge]

Sorry @helske, our system should have caught that one for you. With the above commit you would see this:

library (srr)
packageVersion ("srr")
#> [1] '0.0.1.144'
path <- "/<path>/<to>/bssm"
s <- srr_stats_pre_submit (path)
print (s)
#> [1] "Your code includes the following standard which are not actual standards: [BS7.7]"

^{Created on 2021-11-26 by the reprex package (v2.0.1.9000)}