DOC: for pandas.read_json() using orient='table' add docu about schema spec
Please provide documentation about what kind of type specifications are supported when using the `pandas.read_json()` function with `orient` = 'table'. Currently the [function documentation](https://pandas-docs.github.io/pandas-docs-travis/reference/api/pandas.read_json.html#pandas.read_json) does not even mention 'table' under "The set of possible orients is". There is only a small example in the "Encoding with Table Schema" section.