feat: Add `heading` and `toc_label` options #425

Job	Run time
quality	35s
exclude-test-jobs	1s
tests (ubuntu-latest, 3.9, highest)	37s
tests (ubuntu-latest, 3.9, lowest-direct)	28s
tests (ubuntu-latest, 3.10, highest)	27s
tests (ubuntu-latest, 3.10, lowest-direct)	34s
tests (ubuntu-latest, 3.11, highest)	23s
tests (ubuntu-latest, 3.11, lowest-direct)	27s
tests (ubuntu-latest, 3.12, highest)	35s
tests (ubuntu-latest, 3.12, lowest-direct)	32s
tests (ubuntu-latest, 3.13, highest)	29s
tests (ubuntu-latest, 3.13, lowest-direct)	37s
tests (ubuntu-latest, 3.14, highest)	38s
tests (ubuntu-latest, 3.14, lowest-direct)	38s
tests (macos-latest, 3.9, highest)	41s
tests (macos-latest, 3.10, highest)	53s
tests (macos-latest, 3.11, highest)	45s
tests (macos-latest, 3.12, highest)	28s
tests (macos-latest, 3.13, highest)	34s
tests (macos-latest, 3.14, highest)	52s
tests (windows-latest, 3.9, highest)	50s
tests (windows-latest, 3.10, highest)	49s
tests (windows-latest, 3.11, highest)	48s
tests (windows-latest, 3.12, highest)	51s
tests (windows-latest, 3.13, highest)	1m 39s
tests (windows-latest, 3.14, highest)	1m 59s
	18m 10s

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