Cleans up and clarifies gitignore contribution guidelines

Adds clarification around our expectations for contributions and
how contributions will be handled when they don't meet our requirements.

Updates template to lean into our contribution guidelines.

Cleans up duplicate wording around our contribution guidelines.

README.md

@@ -36,6 +36,9 @@ We support a collection of templates, organized in this way:
 
 ## What makes a good template?
 
+First and foremost, a template contribution must adhere to our
+[Contribution Guidelines](CONTRIBUTING.md).
+
 A template should contain a set of rules to help Git repositories work with a
 specific programming language, framework, tool or environment.
 
@@ -61,33 +64,7 @@ include your language, tool, or project, it’s not because it’s not awesome.
 
 ## Contributing guidelines
 
-We’d love for you to help us improve this project. To help us keep this collection
-high quality, we request that contributions adhere to the following guidelines.
-
-- **Provide a link to the application or project’s homepage**. Unless it’s
-  extremely popular, there’s a chance the maintainers don’t know about or use
-  the language, framework, editor, app, or project your change applies to.
-
-- **Provide links to documentation** supporting the change you’re making.
-  Current, canonical documentation mentioning the files being ignored is best.
-  If documentation isn’t available to support your change, do the best you can
-  to explain what the files being ignored are for.
-
-- **Explain why you’re making a change**. Even if it seems self-evident, please
-  take a sentence or two to tell us why your change or addition should happen.
-  It’s especially helpful to articulate why this change applies to _everyone_
-  who works with the applicable technology, rather than just you or your team.
-
-- **Please consider the scope of your change**. If your change is specific to a
-  certain language or framework, then make sure the change is made to the
-  template for that language or framework, rather than to the template for an
-  editor, tool, or operating system.
-
-- **Please only modify _one template_ per pull request**. This helps keep pull
-  requests and feedback focused on a specific project or technology.
-
-In general, the more you can do to help us understand the change you’re making,
-the more likely we’ll be to accept your contribution quickly.
+Please see our [Contributing Guidelines](CONTRIBUTING.md).
 
 ## Versioned templates
 
@@ -153,3 +130,4 @@ by automatically forking the project and prompting to send a pull request too.
 ## License
 
 [CC0-1.0](./LICENSE).
+