TypeScript/JavaScript docs improvements (#5984)
* use correct language formatter for TypeScript examples
* fixes typo in JS/TS copied from PHP (apparently)
the variables are not named with a prefixed `$`
* fixes bizarre line breaks in markdown examples
* fixes snake case typo to fit JS/TS conventions
* makes example of Uint8Array usage explicit
* removes random extra lines between language blocks
* adds simple example for writing to file in node
* typo: flabuffers => flatbuffers
* adds (previously missing) code blocks to TypeScript code block
* adds context about where `monster_generated` comes from
to the uninitiated, a bit of help like this is welcome