Update README.md with improved image URLs, adjusted preview counts, and refined example data

- Changed image URLs from HTTPS to HTTP for consistency.
- Adjusted preview counts from 10 to 5 in multiple sections for better clarity.
- Updated example neuron data with new IDs and labels.
- Removed redundant rows in various sections to streamline the information presented.
- Enhanced the structure of the preview results for expression patterns and transgene expressions.

Author: Robbie1977