Update raster related episodes to new narratives

[rogerkuou]

In the new episodes order:

• [x] EP5: Satellite data access: Download S2 and DEM data
• [x] EP6: Raster intro
• [x] EP9: Raster data calculation: calculate NDVI from S2 data
• [x] EP10: Parallel computation: compute slope

Issues we have temporary solution and need follow up:

• https://github.com/carpentries-incubator/geospatial-python/issues/120

Issues from upper workflow to see if we can reproduce:

• https://github.com/carpentries-incubator/geospatial-python/issues/153
• https://github.com/carpentries-incubator/geospatial-python/issues/143

Things for consideration:

• https://github.com/carpentries-incubator/geospatial-python/issues/122
• https://github.com/carpentries-incubator/geospatial-python/issues/144
• https://github.com/carpentries-incubator/geospatial-python/issues/145

[rogerkuou]

Hi @fnattino, I realized Zonal Stats should be more vector related. I will move this to #92

[fnattino]

Noticed some updates on the STAC endpoint, may adapt slightly the material depending on https://github.com/Element84/earth-search/issues/31