Add HTMX 2 library

[phillxnet]

As part of rocksor-core issue Reduce JS libs dependencies via HTMX it is required that we first add the HTMX js library itself: to begin centralising/reducing our JS dependencies.

From the HTMX main website we have:

htmx gives you access to AJAX, CSS Transitions, WebSockets and Server Sent Events directly in HTML, using attributes, so you can build modern user interfaces with the simplicity and power of hypertext

Source code: https://github.com/bigskysoftware/htmx

License info re 1.9.8 from unpkg: https://unpkg.com/browse/htmx.org@1.9.8/LICENSE BSD 2-Clause License License from source: https://github.com/bigskysoftware/htmx/blob/master/LICENSE

• SPDX full name "BSD 2-Clause "Simplified" License" reference: BSD-2-Clause

Changelog: https://github.com/bigskysoftware/htmx/blob/master/CHANGELOG.md

README.md: https://github.com/bigskysoftware/htmx#readme

From above readme:

htmx is small (~14k min.gz'd), dependency-free, extendable & IE11 compatible

[phillxnet]

N.B select latest 2.*

https://unpkg.com/browse/htmx.org@2.0.0/ https://unpkg.com/browse/htmx.org@2.0.0/dist/