test

Add a link to the Fatiando Forum in the README #1464

Job	Run time
ubuntu-latest python=3.9 dependencies=oldest	5m 43s
ubuntu-latest python=3.12 dependencies=latest	8m 15s
ubuntu-latest python=3.12 dependencies=optional	8m 39s
macos-latest python=3.12 dependencies=latest	5m 19s
macos-latest python=3.12 dependencies=optional	3m 52s
windows-latest python=3.9 dependencies=oldest	7m 46s
windows-latest python=3.12 dependencies=latest	14m 27s
windows-latest python=3.12 dependencies=optional	14m 28s
macos-13 python=3.9 dependencies=oldest	9m 14s
codecov-upload	8s
	1h 17m 51s

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