Fix spelling of "GitHub" (was "Github")

Author: generalmimon

index.html

@@ -181,7 +181,7 @@ <h4 class="modal-title" id="welcomeModalLabel">Hey there!</h4>
                 <a href="https://gitter.im/kaitai_struct/Lobby" target="_blank">Gitter chatroom</a>.
             </div>
             <div class="form-group">
-                You can view the source code or create issues on Github
+                You can view the source code or create issues on GitHub
                 for the <a href="https://github.com/kaitai-io/kaitai_struct_webide" target="_blank">WebIDE</a> or
                 <a href="https://github.com/kaitai-io/kaitai_struct" target="_blank">Kaitai Struct</a>.
             </div>

src/ui/Parts/AboutModal.html

@@ -24,7 +24,7 @@ <h4 class="modal-title">Hey there!</h4>
                         <a href="https://gitter.im/kaitai_struct/Lobby" target="_blank">Gitter chatroom</a>.
                     </div>
                     <div class="form-group">
-                        You can view the source code or create issues on Github
+                        You can view the source code or create issues on GitHub
                         for the <a href="https://github.com/kaitai-io/kaitai_struct_webide" target="_blank">WebIDE</a> or
                         <a href="https://github.com/kaitai-io/kaitai_struct" target="_blank">Kaitai Struct</a>.
                     </div>