Javascript-install-spfx and Javascript-list-spfx

[DonKirkham]

These are new cross-platform scripts to install any version of SPFx environments.

• Dynamically determines the tools and versions needed, only using a lookup for versions of SPFx that do not have the engine-nodes parameter defined.
• Updated the old script to say Deprecated. It technically still works, but is not being updated for newer versions of SPFx. CHanges to repo:
• Deleted obsolete image assets: Command.png, Results1.png, Results2.png, Results3.png, Results4.png, example.png, preview.png.
• Added new example images: example1.png, example2.png, example3.png, example4.png.
• Updated sample.json metadata: changed name to "spfx-install-js", modified title and descriptions, updated creation and update dates, refined product and category lists, and added new references.
• Updated README.md files for spfx-install-sh and spfx-list-js to include author links and updated visitor stats image URLs.
• Added the list-spfx scripts and supporting files.