docs(readme): readme cleanup with typescript and yarn, move templates…

… to .github folder (#401)

* markdown-ify license

* move issue template to github folder

* split git and npm ignore

* TS and Yarn usage in README

* Revert "markdown-ify license"

This reverts commit 425e8aa.

* Revert "split git and npm ignore"

This reverts commit 53db4f8.

* filter yarn.lock for yarn users

* Address some requested changes

* Finishing touches on README

.gitignore

@@ -2,3 +2,4 @@ node_modules
 coverage
 .DS_Store
 .idea/*
+yarn.lock

README.md

@@ -16,6 +16,9 @@ You can contact us for support on our [chat server](https://discord.gg/V3vSCs7)
 ```js
 const fs = require('fs');
 const ytdl = require('ytdl-core');
+// TypeScript: import ytdl from 'ytdl-core'; with --esModuleInterop
+// TypeScript: import * as ytdl from 'ytdl-core'; with --allowSyntheticDefaultImports
+// TypeScript: import ytdl = require('ytdl-core'); with neither of the above
 
 ytdl('http://www.youtube.com/watch?v=A02s8omM_hI')
   .pipe(fs.createWriteStream('video.flv'));
@@ -157,6 +160,11 @@ For getting started with that, you can look at the `extractActions()` function i
 npm install ytdl-core
 ```
 
+Or for Yarn users:
+```bash
+yarn add ytdl-core
+```
+
 # Tests
 Tests are written with [mocha](https://mochajs.org)