Update README.md

Author: rafaqz

README.md

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 [![Aqua.jl Quality Assurance](https://img.shields.io/badge/Aquajl-%F0%9F%8C%A2-aqua.svg)](https://github.com/JuliaTesting/Aqua.jl)
 
 Rasters.jl defines common types and methods for reading, writing and
-manipulating spatial data. 
+manipulating rasterized spatial data. 
 
 These currently include raster arrays like GeoTIFF and NetCDF, R grd files, 
 multi-layered stacks, and multi-file series of arrays and stacks.