Add OpenCollective sponsor link on the repo page #1129

Job	Run time
Run pre-commit hooks	15s
Pytest on macos-latest with Python 3.6	3m 16s
Pytest on windows-latest with Python 3.6	17m 37s
Pytest on ubuntu-latest with Python 3.7	6m 58s
Pytest on ubuntu-latest with Python 3.9	10m 57s
Pytest on ubuntu-latest with Python 3.11	7m 47s
Pytest on macos-latest with Python 3.7	3m 3s
Pytest on macos-latest with Python 3.9	2m 49s
Pytest on macos-latest with Python 3.11	5m 16s
Pytest on windows-latest with Python 3.7	12m 28s
Pytest on windows-latest with Python 3.9	21m 35s
Pytest on windows-latest with Python 3.11	17m 6s
	1h 49m 7s

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