Fixes#10889.
This involved a bit more refactoring to help-keyman-com.sh in order to
allow for multiple paths to be uploaded.
I opted _not_ to move the entire Keyman Developer documentation into
this repository, partly because a number of pages are still in PHP
rather than Markdown.
When running tests, discovered a number of typos in builder.inc.sh.
Also fixup pathing for builder include for all scripts under resources/
to ensure that we can maximize performance.
Fixes up scripts (except under /linux) to use `#!/usr/bin/env bash`
instead of `#!/bin/bash` or `#!/bin/sh` so that we don't end up with
the ancient version of bash supplied with macOS.
This became urgent with this PR, because of bash-4.xisms in
build-utils.sh, for example on line 572:
```
if [[ -v _builder_params[$e] ]]; then
```
