Increase the visibility of local development document

[ezioruan]

Improve the visibility of local development document

TODO
The testing document should be testing-and-local-development
The page https://fleetdm.com/docs/contributing/testing shows how to do testing and local development which is very great, but the hyperlink title only contains the word testing. add local development will let beginners easily find the document

How?

• [change testing.md to testing-and-local-development.md ]
• [update links on website]

[mike-j-thomas]

I made a PR for this here

[mike-j-thomas]

@ezioruan, thanks for bringing this to our attention. The PR was merged today #6583

[ezioruan]

@mike-j-thomas awesome.