library.properties file - could have an automated check for "include=" field

[RobTillaart]

Description
The library.properties file is used in the CI system.

Today I had a typo (case mismatch) in the field: includes=DHT.h which should be includes=dht.h
It took a while to find the root cause as the error message just said "#include <dht.h> not found.
The very same sketch compiled perfect in the IDE for years so that made me wonder.

Solutions

1. a better error message why the #include is not found, e.g. what is expected.
2. a script that verifies the fields of the library.properties file.
   All mandatory fields are available and correct?
3. document this problem in an FAQ for known error messages
4. ...

[ianfixes]

This seems like a duplicate of #237 , should this just be a comment on that issue?