Add documentation regarding http content length limit
Add documentation regarding http content length limit

Typical error is

    Error while indexing content from [path]: entity content is too long [134161442] for the configured buffer limit [104857600]

Closes #345

dadoonet/fsriver,dadoonet/fscrawler,dadoonet/fsriver,dadoonet/fsriver,dadoonet/fscrawler,dadoonet/fscrawler