Update fontawesome to version 5.8.1

[richard67]

This pull request (PR) updates fontawesome free webfonts to the latest version 5.8.1.

It is a requirement for being able to add new services like e.g. buffer, for which new brand icons have been added recently to fontawesome free.

Since the last update of fontawesome with PR #302 , the structure of the fontawesome npm repository has changed again, so the separate repository for the webfonts has been deprecated, see here: https://www.npmjs.com/package/@fortawesome/fontawesome-free-webfonts.

Instead of this, the repository https://www.npmjs.com/package/@fortawesome/fontawesome-free shall be used.

See upgrading information here: https:/FortAwesome/Font-Awesome/blob/master/UPGRADING.md#50x-to-510.

How to test:

Run the shariff demo site locally on a Linux host which has git and npm installed with the branch of this PR as follows:

$ mkdir shariff-test-pr360
$ cd shariff-test-pr360
$ git clone https:/richard67/shariff-plus.git
$ cd shariff-plus
$ git checkout upstream-update-fontawesome-510
$ git pull origin upstream-update-fontawesome-510
$ npm install
$ npm run build
$ npm run dev

Check the result

1. Check the result in the browser, URL=http://localhost:3000/: Verify that the buttons are shown with the right icons.
2. Download fontawesome free 5.8.1 from here, unpack to some temporary folder and verify that the web fonts files in sub-folder webfonts of that temporary folder are identical with the fonts files in sub-folder dist of the git repository (shariff-test-pr360/shariff-plus).

Clean up after the test

$ cd ../..
$ rm -rf ./shariff-test-pr360

[richard67]

@compeak This could require at least a new minor version number.
If a new major version I am not sure. There a no backwards compatibility breaks or interface changes, so I think a new major version is not necessary.

[compeak]

Thank you.