Add snakemake

[daler]

This adds some support for Snakemake. Since Snakemake is a superset of Python, this copies the existing Python aerial.scm and just adds the ability to navigate rules via aerial.nvim.

I don't quite follow how to make the expected test cases in test/symbols/, so I copied over the Python one to see how the tests break to see if there are any clues...

[daler]

Ah, tests not enabled for PRs, it seems. @stevearc, tests/symbols/snakemake_test.json will definitely need to be fixed, I don't know how to create the expected results.

[stevearc]

Tests are failing because there is no backend detected for the test file. This is because the filetype is not detected. You'll probably need to add another rule here:

aerial.nvim/tests/minimal_init.lua

Lines 9 to 11 in 34b820d

	norg = "norg", -- Neovim doesn't have built-in norg filetype detection
	usd = "usd", -- Neovim doesn't have built-in USD filetype detection
	usda = "usd", -- Neovim doesn't have built-in USD filetype detection

To update the symbols snapshot file, run ./run_tests.sh --update. You'll need to have jq installed and in your PATH.

[daler]

Thanks for the pointer -- tests passing locally now.

[stevearc]

Thanks for the PR!