Add readJson fallback

[JakeSidSmith]

I hope this is acceptable. Re-enabled strict null checks to ensure optional readJson types would not break anything, but this meant updating a few existing bits of code.

Fixes #50

• Re-enable strict null checks (and fix issues)
• Use typeof fs for base file system types
• Fallback to readFile and JSON.parse if readJson is unavailable
• Programatic example with custom file system to test readJson fallback

[jonaskello]

@JakeSidSmith Nice work! Looks good to me, are you ready to merge this?

[JakeSidSmith]

@jonaskello yes, I think it's in a good state. 🙂

Is it okay that my test has made it into the "example"?

I noticed there was a "compile:tests": "tsc -p tests", script, but there is no longer a tests directory?

[jonaskello]

Hmm, yes that's a bit strange :-). I guess that script can be cleaned up and re-added if someone gets the time to introduce unit tests. For now I think the example you made is a good way to test it.

[jonaskello]

Released in 3.3.0.

@JakeSidSmith It would be helpful if you can verify that the new version works as expected both with normal and custom fs :-)

[JakeSidSmith]

My project is currently in a half broken state, so I can't really do a thorough test at the moment, but I can confirm that where previously I was receiving the error below when using fs, memfs and unionfs with version 3.2.0 of tsconfig-paths-webpack-plugin, I am no longer receiving it with version 3.3.0.

I will report back when I have further tested this. 🙂

TypeError: filesystem.readJson is not a function