Autodocsumm

What's Changed
* Fix broken sphinx link in README by cuspymd in https://github.com/Chilipp/autodocsumm/pull/68
* Fix: no links generated in summary table by theOehrly in https://github.com/Chilipp/autodocsumm/pull/70
* improve tests by Chilipp theOehrly in https://github.com/Chilipp/autodocsumm/pull/71, https://github.com/Chilipp/autodocsumm/pull/72, https://github.com/Chilipp/autodocsumm/pull/73

New Contributors
* cuspymd made their first contribution in https://github.com/Chilipp/autodocsumm/pull/68
* theOehrly made their first contribution in https://github.com/Chilipp/autodocsumm/pull/71

**Full Changelog**: https://github.com/Chilipp/autodocsumm/compare/v0.2.7...v0.2.8

This patch fixes some dependency definition (see 63, 64).

This patch resolves some minor deprecation warnings relevant for sphinx 4.0+, and uses the correct license classifier as the license changed to Apache-2.0 in v0.2.5.

This new release changes the license of autodocsumm (which was formerly licensed under GPL-2.0) to Apache-2.0 to make it better usable.

This patch makes `autodocsumm` compatible with `sphinx` 4.0 and from now on requires `python>=3.6`.
Additionally, we implemented support for the `:nosignatures:` option, see https://github.com/Chilipp/autodocsumm/issues/43

This Release makes autodocsumm compatible with sphinx 3.4 and 3.5. See https://github.com/Chilipp/autodocsumm/pull/42