Add CrateDB examples

[esadek]

Closes #53

[ianmcook]

@esadek This is also missing the Java example.

[ianmcook]

Please add the Java example

[esadek]

@ianmcook CrateDB requires the "adbc.postgresql.use_copy" statement option. The JNI driver does not implement AdbcStatement.setOption.

[ianmcook]

@ianmcook CrateDB requires the "adbc.postgresql.use_copy" statement option. The JNI driver does not implement AdbcStatement.setOption.

Ah, ok. I opened apache/arrow-adbc#3868 for this. I also added a simple README explaining why we don't have a CrateDB Java example.