Note git's core.longpaths in CONTRIBUTING (#45069)
Note git's core.longpaths in CONTRIBUTING (#45069)

* Note git's core.longpaths in CONTRIBUTING

So people will be able to clone the repo on Windows.
However, I'm not sure whether this addresses running tests.

* Address PR comments
microsoft/TypeScript,microsoft/TypeScript,Microsoft/TypeScript,microsoft/TypeScript,weswigham/TypeScript,Microsoft/TypeScript,kpreisser/TypeScript,Microsoft/TypeScript,weswigham/TypeScript,kpreisser/TypeScript,weswigham/TypeScript,kpreisser/TypeScript