Add links to Discussion page across website #745
Description
- https://sleap.ai/index.html#learn-to-sleap (in README.rst)
- https://sleap.ai/index.html#contact (in README.rst)
- https://sleap.ai/help.html
- https://sleap.ai/installation.html#getting-help
- https://sleap.ai/api.html (as admonition at the top)