Streamlit-keplergl

- Adds `center_map` and `read_only` arguments
- Fixes issue of data not displayed in map

- Adjusts use of `width` and `height` parameters based on feedback e.g. https://github.com/chrieke/streamlit-keplergl/issues/3
- Removes forced defaults for `width` & `height` parameters
- `height` parameter now correctly supersedes the keplergl figure object setting
- Adds better explanation and more examples
- Removes st component `scrolling` parameter as had no effect