Add a Development section to the README with tips for contributors

[todo]

Because of the layout of the package (single "plugin", `boot.py`, and the result of the code in `src/`) it's recommended to use https://packagecontrol.io/packages/AutomaticPackageReloader so that changes you make during development get picked up without needing to restart ST. Try to format the Python code using https://github.com/psf/black. Be mindful of ST API versions https://www.sublimetext.com/docs/api_reference.html. We support ST3 (build 3211+) for now, but may go ST4 exclusive in the future.

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st3-gitblame/README.md

Lines 50 to 55 in d30f1ae

	@todo Add a Development section to the README with tips for contributors
	@body Because of the layout of the package (single "plugin", `boot.py`, and the result of the code in `src/`) it's recommended to use https://packagecontrol.io/packages/AutomaticPackageReloader so that changes you make during development get picked up without needing to restart ST.
	@body Try to format the Python code using https://github.com/psf/black.
	@body Be mindful of ST API versions https://www.sublimetext.com/docs/api_reference.html. We support ST3 (build 3211+) for now, but may go ST4 exclusive in the future.
	-->

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This issue was generated by todo based on a todo comment in d30f1ae. It's been assigned to @frou because they committed the code.