dev: Development Guide link leads to 404

[JMCulhane]

Update Development Guide link to the 'guides' folder under mango-tango-cli/docs

Currently, the development link in the README.md leads to mango-tango-cli/docs/dev-guide.md which doesn't exist on either main or develop branch.

I've created this issue to track and propose changes for where this link will lead. I propose it simply lead to the docs folder under mango-tango-cli/docs, as mango currently has various folders to keep track of guides for contributing, getting started, and installation for running the CLI.

[KristijanArmeni]

Good catch @JMCulhane. How about we point instead to the Contributor workflow under our Contributing guide in technical docs?

EDIT: While we're at it, the getting started link in our Contributor workflow needs updating too, I created a sub-issue: #222

[KristijanArmeni]

Closed with #239