Support dot in JSON field key #13

Currently, adding something like this in the Log4perl config:

log4perl.appender.DefaultAppender.layout.field.logging.googleapis.com/sourceLocation=%F:%L

will result in a JSON that contains "logging": { "googleapis": { "com/sourceLocation": "..."}} and so it’s not possible to have field names with dot in them.

As far as I know the Log4perl configuration file syntax does not allow to escape dots. This was requested (actually also for use with JSON layout) in this issue but for now the answer was to add the support on the client side.

So would it be possible to add some syntax in this module to support escaping of field names containing dots?