fixed typo

Author: code2k13

docs/index.html

@@ -63,7 +63,7 @@
 
                     <img src="star2k13_video.gif" style="width:100%;max-width: 360px;" /> <br />
 
-                    Starrem2k13, a simple open source for removing stars from deep sky images.
+                    Starrem2k13, a simple open source tool for removing stars from deep sky images.
                     <br />
                     <a class="btn   btn-outline-secondary btn-sm" type="button"
                         href="https://ashishware.com/static/star_removal/index.html">Try Online Demo <i