added note that module currently only works for 8-bit images

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@57332 15284696-431f-4ddb-bdfa-cd5b030d7da7

scripts/i.pansharpen/i.pansharpen.html

@@ -59,6 +59,8 @@ imagery with high resolution panchromatic bands, and lower resolution spectral
 bands include Landsat 7 ETM, QuickBird, and SPOT.
 <br>
 <h2>NOTES</h2>
+The module currently only works for 8-bit images.
+<br><br>
 The command temporarily changes the computational region to the high 
 resolution of the panchromatic band during sharpening calculations, then 
 restores the previous region settings. The current region coordinates (and