Update Help Wanted issue search #1889

Description

The Help Wanted issue search in README.md currently covers several Layer5-related GitHub organizations, but it does not yet include the newly added [blowhorn-ai](https://github.com/blowhorn-ai) organization.

The search link appears in the "Not sure where to start?" section at the bottom of the README as the help-wanted label hyperlink.

This link should be updated to include blowhorn-ai.

Proposed Change

Add the following to the existing search query:

+OR+org%3Ablowhorn-ai

This will include open help wanted issues from the new organization while keeping all existing organizations in the search.

Acceptance Criteria

• Update the help-wanted label hyperlink at the bottom of the README.
• Add +OR+org%3Ablowhorn-ai to the existing search URL.
• Verify that the updated link includes help wanted issues from blowhorn-ai.
• Preserve all existing organizations in the search.