WordPress plugin / shortcode support

[goncharenko]

Feature Request

Create a WordPress plugin or shortcode that makes embedding the HoverBot widget as simple as:

[hoverbot id="your-chatbot-id" key="your-api-key"]```

### Why
WordPress powers ~40% of the web. A one-click plugin install would dramatically lower the barrier to entry.

### Acceptance criteria
- WordPress plugin installable via zip or WP plugin directory
- Shortcode for embedding in any page/post
- Admin settings page for chatbot ID and API key