Add section index to README feature matrix (#1033) (#1034)

Single line of anchor links at the top of the feature matrix for
quick navigation to any of the 18 category sections.

Author: brendancol

README.md

@@ -133,6 +133,8 @@ In the GIS world, rasters are used for representing continuous phenomena (e.g. e
 
 ✅ = native backend    🔄 = accepted (CPU fallback)
 
+[Classification](#classification) · [Diffusion](#diffusion) · [Focal](#focal) · [Morphological](#morphological) · [Fire](#fire) · [Multispectral](#multispectral) · [Multivariate](#multivariate) · [Pathfinding](#pathfinding) · [Proximity](#proximity) · [Reproject / Merge](#reproject--merge) · [Raster / Vector Conversion](#raster--vector-conversion) · [Surface](#surface) · [Hydrology](#hydrology) · [Flood](#flood) · [Interpolation](#interpolation) · [Dasymetric](#dasymetric) · [Zonal](#zonal) · [Utilities](#utilities)
+
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 ### **Classification**