Add event handlers for kay up and down. Disable pan and zoom on pressing ALT. Clean up code (indentations, remove unnecessary `.js`, move react lifecycle methods to the top.)
Add event handlers for kay up and down. Disable pan and zoom on pressing ALT. Clean up code (indentations, remove unnecessary `.js`, move react lifecycle methods to the top.)

hms-dbmi/higlass,hms-dbmi/4DN_matrix-viewer,hms-dbmi/4DN_matrix-viewer,hms-dbmi/higlass,hms-dbmi/higlass,hms-dbmi/higlass,hms-dbmi/4DN_matrix-viewer