feat(Tailwind): add reddit icon to brands pack

[ric-bianchi]

Purpose

The default data/page_sharer.yaml file mentions the icon 'reddit-alien' in the Reddit section (which is commented out by default). However, the above mentioned icon is not found in the 'brands' collection (or in any other collections, as far as I could see).

This PR adds (back) the 'reddit-alien' icon to the brands icon collection, and updates the page_sharer.yaml file to use it.

Screenshots

The newly added Reddit reddit-alien icon in use, on the right:

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[ric-bianchi]

Hi, I just noticed that the newly added reddit-alien icon lacked the fill color, so it did not change its color to white when switching to the dark theme, as shown here below:

Therefore, with my latest commit I added the fill="currentColor" setting to the SVG definition of the icon, so that its line is now correctly set to 'white' when in dark mode, as in the example here below:

[gcushen]

Renamed the icon to simply 'reddit' as in the Tailwind module we use our own SVG icon pack rather than Font Awesome which the Bootstrap module uses, and which contains that longer icon name.

Also, fixed a bug as the PR added an erroneous extra "