Added warning about region not being respected (#1857)

* Added warning about region not being respected

* break lines at approx 70-80 chars

Co-authored-by: Markus Metz <33666869+metzm@users.noreply.github.com>

Co-authored-by: Veronica Andreo <veroandreo@gmail.com>
Co-authored-by: Markus Metz <33666869+metzm@users.noreply.github.com>

imagery/i.landsat.toar/i.landsat.toar.html

@@ -24,6 +24,16 @@ not found in the metadata file then the command line values are used.
 raster is set to null in the output raster and it is not included in
 the equations.
 
+<p>
+<b>Attention</b>: This module does <b>not</b> respect the current 
+region settings, in order to have the largest possible sample of pixels 
+from where to get the darkest one of the scene and perform the DOS 
+correction. To limit the results to a custom region, the user is 
+advised to clip the results (with <a href="r.clip.html">r.clip</a>, for 
+instance) or to define the region first, import the images with region 
+cropping, and then running the module.
+
+
 <h2>Uncorrected at-sensor values (method=uncorrected, default)</h2>
 
 The standard geometric and radiometric corrections result in a