Update README.md

[bkmgit]

Add information on how to install from Git

Platforms affected

Motivation and Context

Makes it easier to install and build the application

Description

Added information on how to clone the repository from Github when creating a Cordova project.

Testing

Tried it out. It still seems that to be able to fully integrate with Git when developing, one will need to create an empty project, remove the folders that are in the Git repository, then clone the Git repository, as explained here https://ccoenraets.github.io/cordova-tutorial/setup-files.html

Checklist

• [ ] I've run the tests to see all new and existing tests pass
• [ ] I added automated test coverage as appropriate for this change
• [ ] Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• [ ] If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• [x] I've updated the documentation if necessary

[dpogue]

My only concern here is whether this is going to cause issues with Apache Software Foundation Policy about not encouraging end users to install packages that have not been voted on and approved for release.

[breautek]

I think the relevant text on that concern is:

Do not include any links on the project website that might encourage non-developers to download and use nightly builds, snapshots, release candidates, or any other similar package.

I think to satisfy that concern, we should replace the git url with an example git repository?

[bkmgit]

It would be good to be able to have the git repository integrate well with Cordova, allowing one to use git pull to get the latest version. Is there some way to specify a specific commit to obtain? If someone is looking at the README.md file, it is likely they are a developer and having example information on how to integrate their project with version control is helpful.