General & modular STAC catalogs + COP30 (#3)

* Created collections.py to store STAC catalog endpoints and symbology preferences
* Updated stac.py accordingly with geberalized STAC search and load functions
* Added support for COP30 (force multidirectional hillshade)
    * Custom NumPy hillshade functions to avoid gdal python API dependency
* Fixed issue where changing the basemap would clear controls for raster COGs

Author: Jack-Hayes

README.md

@@ -6,6 +6,10 @@
 
 Draw a box anywhere on Earth and explore RGB (Sentinel‑2), SAR (Sentinel‑1), and contextual layers (ESA WorldCover). PlanetQuery is a purely Python-based web map explorer that leverages open STAC catalogs and Cloud-Optimized GeoTIFFs (COGs). Support for additional STAC catalogs is in progress.
 
+Credit to [@scottyhq](https://github.com/scottyhq), [@gbrencher](https://github.com/gbrencher), and [@egagli](https://github.com/egagli) for inspiration and code logic. 
+
+Many thanks to banesullivan's [localtileserver](https://github.com/banesullivan/localtileserver) package and 'issue' replies
+
 ## Try it in your browser (no install)
 
 <a href="https://mybinder.org/v2/gh/Jack-Hayes/planetquery/main?urlpath=/voila/render/notebooks/app.ipynb" target="_blank" rel="noopener noreferrer">