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

css/reveal.scss

@@ -1805,8 +1805,7 @@ $notesWidthPercent: 25%;
 	top: 15px;
 	left: 15px;
 	z-index: 30;
-	transition: all 400ms ease;
-	font-size: 18px;
+	font-size: 32px;
 	-webkit-tap-highlight-color: rgba( 0, 0, 0, 0 );
 }
 
@@ -1815,7 +1814,13 @@ $notesWidthPercent: 25%;
 	padding: 8px;
 	font-size: inherit;
 	color: currentColor;
-	border: 1px solid currentColor;
+	border: 0;
+}
+.reveal.has-dark-background .jump-to-slide-input {
+	color: #fff;
+}
+.reveal.has-light-background .jump-to-slide-input {
+	color: #222;
 }
 
 .reveal .jump-to-slide-input:focus {

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';
 
 	}