add jump-to-slide to help overlay, style tweaks

js/controllers/jumptoslide.js

@@ -55,6 +55,9 @@ export default class JumpToSlide {
 
 	}
 
+	/**
+	 * Parses the current input and jumps to the given slide.
+	 */
 	jump() {
 
 		const value = this.jumpInput.value.trim( '' );

js/controllers/keyboard.js

@@ -43,6 +43,7 @@ export default class Keyboard {
 		this.shortcuts['Shift + ←/&#8593/→/↓']      = 'Jump to first/last slide';
 		this.shortcuts['B  ,  .']                       = 'Pause';
 		this.shortcuts['F']                             = 'Fullscreen';
+		this.shortcuts['G']                             = 'Jump to slide';
 		this.shortcuts['ESC, O']                        = 'Slide overview';
 
 	}