Geojson-client

* Removed unnecessary depdendency `pytz` (thanks scop).

* Removed integration with NSW Rural Fire Service, please use async library https://github.com/exxamalte/python-aio-geojson-nsw-rfs-incidents instead.
* Added Python 3.10 support.
* Removed Python 3.6 support.
* Bumped library versions: black, flake8, isort.
* General code improvements.
* Migrated to github actions.

* Allow overriding filters on update (with backwards compatibility).
* Add default `Accept-Encoding: deflate, gzip` request header.
* Added Python 3.9 support.
* Code housekeeping (black formatting, isort, flake8).

* Added Python 3.8 support.
* Drop Python 3.5 support.
* Excluded tests from package.

* Fetch NSW Rural Fire Service feed securely via HTTPS (thanks davidjb).
* Provide last timestamp from NSW Rural Fire Service feed entries.

* Simple Feed Manager for all feeds added.
* Feed update extracts timestamp in preparation for more sophisticated feed management.
* Third-party library updates.