move templates to .github folder

Summary:
This moves the Template files to the .github folder. This helps clear up the extra files in the root of the directory.

This is my first PR 😄  and I plan to contribute more to this awesome project.
Closes https://github.com/facebook/react-native/pull/7854

Differential Revision: D3424679

fbshipit-source-id: 2baca0bb4182eb6d803836e10a5434d980e7d0c3

.github/ISSUE_TEMPLATE.md

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+Hey there and thank you for using React Native!
+
+React Native, as you've probably heard, is getting really popular and truth is we're getting a bit overwhelmed by the activity surrounding it. There are just too many issues for us to manage properly.
+
+Do the checklist before filing an issue:
+
+- [ ] Is this something you can **debug and fix**? Send a pull request! Bug fixes and documentation fixes are welcome.
+- [ ] Have a usage question? Ask your question on [StackOverflow](http://stackoverflow.com/questions/tagged/react-native). We use StackOverflow for usage question and GitHub for bugs.
+- [ ] Have an idea for a feature? Post the feature request on [Product Pains](https://productpains.com/product/react-native/). It has a voting system to surface the important issues. GitHub issues should only be used for bugs.
+
+
+None of the above, create a bug report
+------------------------------------------------------------------
+
+Make sure to add **all the information needed to understand the bug** so that someone can help. If the info is missing we'll add the 'Needs more information' label and close the issue until there is enough information.
+
+- [ ] Provide a **minimal code snippet** / [rnplay](https://rnplay.org/) example that reproduces the bug.
+- [ ] Provide **screenshots** where appropriate
+- [ ] What's the **version** of React Native you're using?
+- [ ] Does this occur on iOS, Android or both?
+- [ ] Are you using Mac, Linux or Windows?

.github/PULL_REQUEST_TEMPLATE.md

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+Thanks for submitting a pull request! Please provide enough information so that others can review your pull request:
+
+(You can skip this if you're fixing a typo or adding an app to the Showcase.)
+
+Explain the **motivation** for making this change. What existing problem does the pull request solve?
+
+Prefer **small pull requests**. These are much easier to review and more likely to get merged. Make sure the PR does only one thing, otherwise please split it.
+
+**Test plan (required)**
+
+Demonstrate the code is solid. Example: The exact commands you ran and their output, screenshots / videos if the pull request changes UI.
+
+Make sure tests pass on both Travis and Circle CI.
+
+**Code formatting**
+
+Look around. Match the style of the rest of the codebase. See also the simple [style guide](https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md#style-guide).
+
+For more info, see the ["Pull Requests" section of our "Contributing" guidelines](https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md#pull-requests).