docs: update fedora media writer link on installation page

[RaduAvramescu]

On the installation page (https://docs.projectbluefin.io/installation) there is the following text:

Use the Fedora Media Writer to create installation media

The Fedora Media Writer link currently leads to the flathub page for Fedora Media Writer. I don't think this is ideal because of 3 reasons:

• Flatpak is not OS agnostic
• The flathub page provides very limited information about Fedora Media Writer
• Usage instructions are lacking

This link should be more appropriate: https://docs.fedoraproject.org/en-US/fedora/latest/preparing-boot-media/#_fedora_media_writer

The link above fixes the above 3 issues as such:

• It provides installation instructions for Linux, Windows and MacOS
• It documents what Fedora Media Writer is and does in a better way
• It contains usage instructions

[RaduAvramescu]

As an additional note, after building and running the application locally with npm I encountered these files that were picked up by git as modified:

• static/data/playlist-metadata.json
• static/feeds/bluefin-releases.json

I did not include those files in the commit as the changes are unrelated. I just thought it might be worthwhile to note this.