layouts: Fix more structured data escaping issues

I think we actually only need to quote string literals. Otherwise,
it seems that Hugo automatically adds quoting for us, and doesn't
use funny escaping of URLs, special characters, etc.
Version 1.4.1

And oops, I had forgotten to bump the version in package.json for
CHANGELOG.md: Add note about fix for structured data
layouts: Remove quoting of structured data

I don't understand it, but quoting these values causes Hugo to use
escape codes for non-ASCII (?) characters. For example:

  "description": "A thriving oasis in Jordan\x27s desert is at risk of disappearing."

Google's Search Console shows the following error:

    Unparsable structured data > Bad escape sequence in string

We had a similar issue with dates that was fixed in #111 and the
solution is the same here.
README.md: Add note about Farsi
CHANGELOG.md: Add note about updated dependencies
Regenerate static assets
Run npm update

Brings new versions of rtlcss, webpack, and fontawesome.
CHANGELOG.md: Adjust headings
CHANGELOG.md: Release v1.4.0
CHANGELOG.md: Update notes for unreleased version
layouts/partials/meta-terms.html: Trailing slash

Hard code a trailing slash in URLs for categories and tags to avoid
an HTTP 301 redirect at the very least, and an HTTP 404 at the very
worst (depending on web server configuration).

This is a workaround for a problem caused by our manual construction
of URLs using the categories and tags strings in post front matter.
Hugo's own taxonomy tooling always uses a trailing slash.

See: https://github.com/alanorth/hugo-theme-bootstrap4-blog/issues/128
Use Font Awesome SVGs via JavaScript

This is a bit of "one step forward, two steps back" in that we are
now using the much more lean SVG icons—and only the ones we are ac
tually using—instead of having to download the two ~70KiB web font
files, but it means we need to use JavaScript.

This approache was inspired by the work @xekon did in #127.

See: https://fontawesome.com/how-to-use/on-the-web/advanced/svg-javascript-core
See: https://github.com/alanorth/hugo-theme-bootstrap4-blog/pull/127
CHANGELOG.md: Add note about Font Awesome 5
Regenerate static assets
Update to Font Awesome 5

Nothing really new as far as how we're using Font Awesome, but it is
good to keep up with the times and the tooling. Users that have used
custom fonts in their content or layouts will need to update their
icon prefixes from "fa" to "fas" or "fab" depending on which font
their icon comes from.

See: https://fontawesome.com/how-to-use/on-the-web/setup/upgrading-from-version-4
Regenerate static assets
source/scss/font-awesome.scss: Remove Google+ icon
CHANGELOG.md: Add note about Google Plus
layouts: Remove a few more references to GooglePlus

The sharing icons were removed in 2019, but these remained.