Update contribution link in README

[rashenck]

The link for first-time contributors in the repo README is updated

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[rmartin16]

FWIW, I had thought that linking to latest instead of stable made more sense for these purposes. The contribution guide is not as inherently tied to the version of Toga as the rest of the docs are; therefore, directing new contributors to the latest documentation for how to contribute ensures they are reading the most up-to-date information.

[rashenck]

FWIW, I had thought that linking to latest instead of stable made more sense for these purposes. The contribution guide is not as inherently tied to the version of Toga as the rest of the docs are; therefore, directing new contributors to the latest documentation for how to contribute ensures they are reading the most up-to-date information.

Thanks for the feedback - makes perfect sense why you'd want to onboard folks with latest then!