developer_docs.md: Update new version instructions #624

	name: MD Format
	on: [push, pull_request]

	jobs:
	mdformat:
	name: Mdformat Action
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- name: Setup python
	uses: actions/setup-python@v2
	with:
	python-version: 3.9
	architecture: x64
	- uses: actions/cache@v1
	with:
	path: ~/.cache/pip
	key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
	- run: pip install -r requirements.txt
	- run: mdformat --check docs

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