Add self-test feature to test file-readability on the fly based on user demand

Already added a prototype/working version in cae10c0

This is to test read functions capabilities for various file types.

A broader framework can be adopted here to make almost all tests available to the user through appropriate channels.

The idea is that a test will be conditional when there is a heavy dependency on the system or third-party library. But user should have an option to run these tests for debugging/knowing machine issues. A guide also can be made for raising the issue in Github for the same.

This can be implemented by adopting tests that were already written.

As of now, a separate function is written for a test.

tidycells/R/possible_to_support.R

Line 205 in cae10c0

possible_to_support_real_file_type_checks <- function() {