fix typo, it's "usage"

Change-Id: I283f20a447bf78133503f0750f9e36bb4f86bb3f

faq/faq.md

@@ -233,7 +233,7 @@ There's different ways depending on your needs and personal setup:
 
     **Note**  
     - Requires Photobooth v2.11.0 or later!
-    - There's a delay of about 3 seconds until the preview starts, to avoid that disable the `Battery saving mode on gphoto2 live preview` option to generate a preview in background. **This results in a high battery usagage and also a general slowdown.**
+    - There's a delay of about 3 seconds until the preview starts, to avoid that disable the `Battery saving mode on gphoto2 live preview` option to generate a preview in background. **This results in a high battery usage and also a general slowdown.**
     - Sometimes Chromium doesn't detect the V4l2 camera launch from php: you need to run `sudo gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video0` from terminal first and load chrome a first time with a webpage asking for the camera.
     - Chromium sometimes has trouble, if there is another webcam like `bcm2835-isp`, it will take it by default instead. Disable other webcams, e.g. `rmmod bcm2835-isp`
     - Make sure the countdown is long enough to start the preview and free gphoto2 at the end of the countdown to be able to take a picture (2 seconds before the countdown ends)

manual/faq.html

@@ -280,7 +280,7 @@ <h3>How to use a live stream as background at countdown?</h3>
 <p><strong>Note</strong>  </p>
 
 <ul><li>Requires Photobooth v2.11.0 or later!</li>
-<li>There's a delay of about 3 seconds until the preview starts, to avoid that disable the <code>Battery saving mode on gphoto2 live preview</code> option to generate a preview in background. <strong>This results in a high battery usagage and also a general slowdown.</strong></li>
+<li>There's a delay of about 3 seconds until the preview starts, to avoid that disable the <code>Battery saving mode on gphoto2 live preview</code> option to generate a preview in background. <strong>This results in a high battery usage and also a general slowdown.</strong></li>
 <li>Sometimes Chromium doesn't detect the V4l2 camera launch from php: you need to run <code>sudo gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video0</code> from terminal first and load chrome a first time with a webpage asking for the camera.</li>
 <li>Chromium sometimes has trouble, if there is another webcam like <code>bcm2835-isp</code>, it will take it by default instead. Disable other webcams, e.g. <code>rmmod bcm2835-isp</code></li>
 <li>Make sure the countdown is long enough to start the preview and free gphoto2 at the end of the countdown to be able to take a picture (2 seconds before the countdown ends)

resources/lang/en.json

@@ -204,7 +204,7 @@
   "manual_previewCamFlipHorizontal": "If enabled, preview from device cam is flipped horizontal.",
   "manual_previewCamTakesPic": "If enabled, a picture is taken from device cam instead executing the \"Take picture command\". Please note that the resolution depends on the given hight and width because it's acts like taking a screenshot.",
   "manual_preview_camera_mode": "Choose between front- or back facing camera mode of your device cam.",
-  "manual_preview_gphoto_bsm": "If enabled, gphoto2 live preview is started once a photo get triggered. This results in a delay of ~3 seconds until the preview is visible at countdown. If disabled, a preview is generated in background which results in a high battery usagage and also a general slowdown.",
+  "manual_preview_gphoto_bsm": "If enabled, gphoto2 live preview is started once a photo get triggered. This results in a delay of ~3 seconds until the preview is visible at countdown. If disabled, a preview is generated in background which results in a high battery usage and also a general slowdown.",
   "manual_preview_ipCamPreviewRotation": "Choose to rotate the preview from URL.",
   "manual_preview_ipCamURL": "CSS style to use a stream from an URL for preview while countdown. <p>Example: <code>url(../img/bg_bluegray.jpg)</code></p>",
   "manual_preview_mode": "Choose a live preview mode. By default live preview is disabled, you can choose between a preview at countdown by your device cam and a preview from a URL. Preview \"from device cam\" will always use the camera of the device where Photobooth get opened in a Browser (e.g. on a tablet it will always show the tablet camera while on a smartphone it will always show the smartphone camera instead)! A secure origin or exception is required! You can find out how to set an exception <a href=\"https://medium.com/@Carmichaelize/enabling-the-microphone-camera-in-chrome-for-local-unsecure-origins-9c90c3149339\"  target=\"_blank\">here</a>.",