TypeScript docs (#4680)

* Eclipse ignore

* TypeScript support

* Prefixing enums

* Test results

* Merged JS and TS generators

* Fixed AppVeyor build problems

* Fixed more AppVeyor build problems

* Fixed more AppVeyor build problems

* Changed TS flag to options struct

* Storing options by value

* Removed unneeded const

* Re-export support for unions

* Uint support

* Casting bools to numbers for mutation

* TS shell tests

* Reverted generates js test file to original version

* Backing up js tests and properly generating test data

* Not importing flatbuffers for TS test generation

* Not overwriting generated js for tests

* AppVeyor test fixes

* Generating the most strict TS code possible

* Not returning null when creating vectors

* Not returning null from struct contructors

* Vector of unions for ts/js

* Sanity check for languages

* Indentation fix + output test files

* Vectors of unions for php

* Fixes to union vector handling + tests

* Fix for strictPropertyInitialization

* Fix for new aligned operator new for gcc >= 7.1

* Not generating imports/ns prefixes with --gen-all

* TypeScript docs

docs/source/TypeScriptUsage.md

@@ -0,0 +1,66 @@
+Use in TypeScript    {#flatbuffers_guide_use_typescript}
+=================
+
+## Before you get started
+
+Before diving into the FlatBuffers usage in TypeScript, it should be noted that
+the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide to
+general FlatBuffers usage in all of the supported languages
+(including TypeScript). This page is specifically designed to cover the nuances
+of FlatBuffers usage in TypeScript.
+
+You should also have read the [Building](@ref flatbuffers_guide_building)
+documentation to build `flatc` and should be familiar with
+[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
+[Writing a schema](@ref flatbuffers_guide_writing_schema).
+
+## FlatBuffers TypeScript library code location
+
+The code for the FlatBuffers TypeScript library can be found at
+`flatbuffers/js` with typings available at @types/flatubffers.
+
+## Testing the FlatBuffers TypeScript library
+
+To run the tests, use the [TypeScriptTest.sh](https://github.com/google/
+flatbuffers/blob/master/tests/TypeScriptTest.sh) shell script.
+
+*Note: The TypeScript test file requires [Node.js](https://nodejs.org/en/).*
+
+## Using the FlatBuffers TypeScript libary
+
+*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
+example of how to use FlatBuffers in TypeScript.*
+
+FlatBuffers supports both reading and writing FlatBuffers in TypeScript.
+
+To use FlatBuffers in your own code, first generate TypeScript classes from your
+schema with the `--ts` option to `flatc`. Then you can include both FlatBuffers
+and the generated code to read or write a FlatBuffer.
+
+For example, here is how you would read a FlatBuffer binary file in TypeScript:
+First, include the library and generated code. Then read the file into an
+`Uint8Array`. Make a `flatbuffers.ByteBuffer` out of the `Uint8Array`, and pass
+the ByteBuffer to the `getRootAsMonster` function.
+
+~~~{.ts}
+  // note: import flabuffers with your desired import method
+
+  import { MyGame } from './monster_generated';
+
+  let data = new Uint8Array(fs.readFileSync('monster.dat'));
+  let buf = new flatbuffers.ByteBuffer(data);
+
+  let monster = MyGame.Example.Monster.getRootAsMonster(buf);
+~~~
+
+Now you can access values like this:
+
+~~~{.ts}
+  let hp = monster.hp();
+  let pos = monster.pos();
+~~~
+
+## Text parsing FlatBuffers in TypeScript
+
+There currently is no support for parsing text (Schema's and JSON) directly
+from TypeScript.