chore: Add 'aria-label' for Table of Contents component

[rschristian]

Fiddling with Algolia and went to exclude the ToC from indexing and realized we don't have any label for it at the moment.

Potentially could add a real label, though I think it's unnecessary. We should have an aria-label for it though at the least

Edit: On second thought, all of our nav areas should have aria labels. Will fix.

[github-actions]

Size Change: +13 B (0%)

Total Size: 449 kB

ℹ️ View Unchanged

Filename	Size	Change
build/assets/blog-page-********.js	257 B	0 B
build/assets/docsearch-********.js	28.9 kB	+1 B (0%)
build/assets/errors-********.js	342 B	0 B
build/assets/index-********.js	32.6 kB	+12 B (+0.04%)
build/assets/index-********.css	9.65 kB	0 B
build/assets/repl-********.css	1.51 kB	0 B
build/assets/repl-********.js	148 kB	0 B
build/assets/repl-page-********.js	7.65 kB	0 B
build/assets/repl.worker-********.js	213 kB	0 B
build/assets/style-********.css	3.07 kB	0 B
build/assets/style.module-********.js	159 B	0 B
build/assets/tutorial-page-********.js	1.99 kB	0 B
build/assets/tutorial-page-********.css	1.76 kB	0 B

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