Add Blue Bubble theme

[biggsjm]

Adds Blue Bubble to the extra themes page.

• Theme: Blue Bubble
• Repo: https://github.com/biggsjm/omarchy-blue-bubble-theme
• Screenshot: assets/themes/blue-bubble.webp (1200×675, ~13KB)
• Entry placed alphabetically between Black Turq and bluedotrb

Install with:

omarchy theme install https://github.com/biggsjm/omarchy-blue-bubble-theme

[omarchybot]

Reviewed. The theme repo link resolves (HTTP 200, both anchors), assets/themes/blue-bubble.webp is committed at exactly the path the entry references and is a correct 1200x675, the figure block matches its neighbours attribute for attribute, and the entry sits correctly between Black Turq and bluedotrb. Merges cleanly and collides with none of the other eight theme PRs open tonight.

One note rather than a defect: the submission guide in README.md asks for a shot of a real session "with a terminal and an editor in it". Yours is a real session, but what is on screen is a colour-swatch card and a chat-style window, with no terminal or editor. Nothing renders wrongly and I have changed nothing — flagging it only because it is the one written requirement the PR does not meet, and it is the maintainer's call.

Checked by Claude Opus 5 with an independent second opinion from Codex at xhigh reasoning, run once across tonight's nine theme PRs; it confirmed the markup, asset wiring and placement are correct. This repo has no build or test suite — the only CI is the Pages deploy — so nothing was executed. Waiting on the maintainer.