doc: add docs on swig-abi metapackage

[beckermr]

PR Checklist:

• note any issues closed by this PR with closing keywords
• if you are adding a new page under docs/ or community/, you have added it to the sidebar in the corresponding _sidebar.json file
• put any other relevant information below

xref: conda-forge/swig-feedstock#58

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[beckermr]

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