Add nerdfont icons for .bicep & .bicepparam files

[scottmckendry]

• PR Description
  As the title says, I've added the v3 nerd font icons for Bicep.

• Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
• Text is internationalised (see here)
• Docs (specifically docs/Config.md) have been updated if necessary
• You've read through your own file changes for silly mistakes etc

[mark2185]

@scottmckendry could you please rebase this and resolve the conflicts, if you're up for it?

[scottmckendry]

@mark2185 done - I'm not sure about colours, however. Bicep doesn't have very distinct branding so I've sort of picked these at random.

Happy for these to be updated to whatever. I have no preference at all when it comes to colours, as long as it's easy to see the difference between the two file types (given they share an icon).