Add PEP-561 with py.typed #38

Job	Run time
Test on ubuntu-latest / Python 3.8	24s
Test on ubuntu-latest / Python 3.9	26s
Test on ubuntu-latest / Python 3.10	31s
Test on ubuntu-latest / Python 3.11	30s
Test on ubuntu-latest / Python 3.12	38s
Test on ubuntu-latest / Python pypy-3.8	26s
Test on ubuntu-latest / Python pypy-3.9	26s
Test on ubuntu-latest / Python pypy-3.10	24s
Test on windows-latest / Python 3.8	40s
Test on windows-latest / Python 3.9	44s
Test on windows-latest / Python 3.10	39s
Test on windows-latest / Python 3.11	57s
Test on windows-latest / Python 3.12	1m 45s
Test on windows-latest / Python pypy-3.8	1m 51s
Test on windows-latest / Python pypy-3.9	1m 25s
Test on windows-latest / Python pypy-3.10	1m 59s
Test on macos-latest / Python 3.10	41s
Test on macos-latest / Python 3.11	36s
Test on macos-latest / Python 3.12	1m 12s
	16m 14s

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