Add touch gestures section to README.md

Author: Weera Wu

README.md

@@ -25,7 +25,8 @@ A Keynote-inspired presentation app written with Mithril
 
 3. Using a browser, go to `http://localhost:8000` and you'll see example slides.
 
-4. To add or edit slides, make changes to the `slides.json` file and reload your browser.
+4. To add or edit slides, make changes to the `slides.json` file and reload your
+   browser.
 
 ## Keyboard shortcuts
 Shortcuts for navigating slides are listed below.
@@ -38,25 +39,34 @@ Quit presentation mode    | <kbd>Esc</kbd> or <kbd>Q</kbd>
 Show or hide the pointer  | <kbd>C</kbd>
 Change presentation theme | <kbd>T</kbd>
 
+## Touch gestures
+Gestures for navigating slides on touchscreen devices.
+
+Action                    | Gesture
+------------------------- | --------------------------------------------
+Advance to the next slide | Tap on the right
+Go to previous slide      | Tap on the left
+Change presentation theme | Touch and hold
+
 ## Offline mode
-mithril-slides requires an internet connection to work. If you are to present in a
-place without one. You can still use mithril-slides by checking out `offline` branch
-before starting a web server:
+mithril-slides requires an internet connection to work. If you are to present in
+a place without one. You can still use mithril-slides by checking out `offline`
+branch before starting a web server:
 
         $ git checkout offline
         $ python -m SimpleHTTPServer 8000       # Python 2
         $ python -m http.server 8000            # Python 3
 
-You also need to change src properties of all image and embed objects in your
-`slides.json` file to local files.
+You also need to point the `src` property of all images and embed objects in
+your `slides.json` file to local files.
 
 ## Known issues
 Some websites can not be embedded because they have secure HTTP headers (either
-`X-Frame-Options` or `Content-Security-Policy`) set in their responses. To remove
-those headers, you need a browser extension. For Google Chrome, install
+`X-Frame-Options` or `Content-Security-Policy`) set in their responses. To
+remove those headers, you need a browser extension. For Google Chrome, install
 [ModHeader][1] extension and add response headers for above headers with empty
-values. For Firefox, install [Modify Response Headers][2] add-on and add filters for
-those headers. The following slide can be used to test your setup:
+values. For Firefox, install [Modify Response Headers][2] add-on and add filters
+for those headers. The following slide can be used to test your setup:
 
         {
             "embed": {