DOC: Move all docs into en/ subdirectory (#1505)

* DOC: Move all docs into en/ subdirectory

PR #1502 is working on adding a Chinese translation to the docs. In
general, I encouraged this (in #1452) as a path towards getting useful
translated content in the game without requiring a massive
refactor/rearchitecting of everything.

To support this, this takes the first step of moving our docs into an
en/ subdirectory, so that other languages can live alongside. No effort
is made at this time to support or select between alternate languages;
this is a pure-rename refactor.

src/Documentation/doc/en/programming/learn.md

@@ -0,0 +1,35 @@
+# Learn to Program in JavaScript
+
+## For Beginner Programmers
+
+If you have little to no programming experience, that's okay!
+You don't need to be a great programmer in order to enjoy or play this game.
+In fact, this game could help you learn some basic programming concepts.
+
+Here are some good tutorials for learning programming/JavaScript as a beginner:
+
+- [Learn-JS](https://www.learn-js.org/en/Welcome)
+- [programiz](https://www.programiz.com/javascript/get-started)
+- [Speaking JavaScript](https://exploringjs.com/es5/)
+  This is a bit on the longer side.
+  You can skip all of the historical background stuff.
+  Recommended chapters: 1, 7-18
+
+## For Experienced Programmers
+
+The following section lists several good tutorials/resources for those who have experience programming but who have not worked extensively with JavaScript before.
+
+Before that, however, it's important to clarify some terminology about the different versions of JavaScript.
+These are summarized in this article:
+
+[WTF is ES6, ES8, ES2017, ECMAScript...](https://codeburst.io/javascript-wtf-is-es6-es8-es-2017-ecmascript-dca859e4821c)
+
+An important takeaway from this article is that ES6, also known as ES2015, introduced many major features that are commonly seen in modern JavaScript programming.
+However, this means that ES5 engines and interpreters will fail if they encounters these ES6 features.
+You'll see why this is important further down.
+
+- [MDN Introduction to JS](https://developer.mozilla.org/en-US/docs/Web/JavaScript/A_re-introduction_to_JavaScript)
+- [Eloquent JavaScript (ES6+)](https://eloquentjavascript.net/)
+  Recommended Chapters: Introduction, 1-6
+- [Modern JavaScript Tutorial (ES6+)](https://javascript.info/)
+  Recommended Chapters: 2, 4-6