Update README

[JT-39]

Is your feature request related to a problem? Please describe.
Having just started using the template, I cam across a few issues which may affect others. I think it would be good if the solutions to these were included in the README (to also avoid lots of the same questions).

Describe the solution you'd like
An acknowledgement of the issue "shinytest2 - Invalid path to Chrome (chromote) error message" addressed in the DfE Analysts’ Guide. Maybe a link to the solution.

Also, explaining an error one may come across when running shinytest2::test_app() after having changed the app title. In the server.R there is an observe() which changes the app title based on a selection. This means the app title is unlikely to match the test and result in a failed test.

Describe alternatives you've considered
Links to these in the DfE Analysts’ Guide.