Add Audio Hijack to the streaming software guide.

[pjaudiomv]

Fixes issue:

N/A

Proposed changes:

• Add an Audio Hijack section to the Streaming Software user guide (src/content/docs/docs/user-guide/streaming-software.md).
• Document connecting Audio Hijack's Broadcast block to AzuraCast via Icecast, with the AzuraCast "Streamers/DJ Accounts"
  connection-info mapping.
• Include a setup screenshot (src/content/docs/docs/images/streaming-software/audiohijack.png) and an optional note on the Metadata
  tab.
• Link to Rogue Amoeba's Audio Hijack product page and official manual.

Disclosure:

• I'm simply a user of Audio Hijack and am not affiliated with Rogue Amoeba Software. This contribution is based on my own experience using the software with AzuraCast.

[pjaudiomv]

Hey @BusterNeece can we get some eyes on this whenever you get a chance