increment @folio/stripes to v5

Increment the package's dependency on stripes from v4 to v5, which also requires incrementing react-router from v4.0 to v5.2.

v5 has been present in the folio-snapshot and folio-testing builds since 2020-06-30, which demonstrates that it works, but since @folio/stripes is only a peer-dep at the app level, this means unit-tests have continued to run against v4 and may need to be updated for v5.