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/index.md

@@ -0,0 +1,63 @@
+# Documentation
+
+## Guides
+
+- [Beginner's guide](help/getting_started.md)
+
+## Basic Mechanics
+
+- [Stats](basic/stats.md)
+- [Terminal](basic/terminal.md)
+- [Hacking](basic/hacking.md)
+- [Scripts](basic/scripts.md)
+- [Servers](basic/servers.md)
+- [RAM](basic/ram.md)
+- [Hacknet nodes](basic/hacknet_nodes.md)
+- [Augmentations](basic/augmentations.md)
+- [Companies](basic/companies.md)
+- [Factions](basic/factions.md)
+- [Crimes](basic/crimes.md)
+- [Infiltration](basic/infiltration.md)
+- [Programs](basic/programs.md)
+- [Reputation](basic/reputation.md)
+- [Stock market](basic/stockmarket.md)
+- [World](basic/world.md)
+- [Coding contracts](basic/codingcontracts.md)
+- [Autocomplete](basic/autocomplete.md)
+
+## Advanced Mechanics
+
+- [Hacking algorithms](programming/hackingalgorithms.md)
+- [List of factions and their requirements](advanced/faction_list.md)
+- [Offline scripts and bonus time](advanced/offlineandbonustime.md)
+- [BitNodes](advanced/bitnodes.md)
+- [BitNode recommendation - Short guide](advanced/bitnode_recommendation_short_guide.md)
+- [BitNode recommendation - Comprehensive guide](advanced/bitnode_recommendation_comprehensive_guide.md)
+- [Source-Files](advanced/sourcefiles.md)
+- [Gang](advanced/gang.md)
+- [Corporation](advanced/corporations.md)
+- [Intelligence](advanced/intelligence.md)
+- [Bladeburner](advanced/bladeburners.md)
+- [Hacknet servers](advanced/hacknetservers.md)
+- [Sleeves](advanced/sleeves.md)
+- [Grafting](advanced/grafting.md)
+- [Stanek's Gift](advanced/stanek.md)
+- [IPvGO](programming/go_algorithms.md)
+
+## Resources
+
+- [NS API documentation](https://github.com/bitburner-official/bitburner-src/blob/stable/markdown/bitburner.ns.md)
+- [Learn to program](programming/learn.md)
+- [Remote API](programming/remote_api.md)
+- [Game frozen or stuck?](programming/game_frozen.md)
+- [React](programming/react.md)
+- [Tools & Resources](help/tools_and_resources.md)
+- [Changelog](changelog.md)
+- [Changelog - Legacy v1](changelog-v1.md)
+- [Changelog - Legacy v0](changelog-v0.md)
+
+## Migration
+
+- [Bitburner v1.0.0 script migration guide](migrations/v1.md)
+- [Bitburner v2.0.0 script migration guide](migrations/v2.md)
+- [Netscript 2 migration guide (.script to .js)](migrations/ns2.md)