can publish-spa support publish with theme data installed from thememarket

If i want to publish logseq with a theme, now the only way to custom my css style is editing `custom.css`.
Can this repo support ability to publish with theme installed from theme market?

Maybe can add a config field like this:
```
- with
- theme: xxx
```

Start by reading the publish-spa configuration handling and the GitHub Action/CLI publishing flow to determine where theme-market data could enter the published SPA. Done means a documented configuration can select an installed theme and the resulting published Logseq graph uses that theme without editing custom.css.

Written by the indexing model from the issue text.