Add step to switch context

wiki/src/install/expert/usb.mdwn

@@ -116,3 +116,5 @@ using the Tails signing key.
 [[!inline pages="install/inc/steps/install_tails_installer.inline" raw="yes"]]
 
 [[!inline pages="install/inc/steps/install_final.inline" raw="yes"]]
+
+[[!inline pages="install/inc/steps/switch.inline" raw="yes"]]

wiki/src/install/inc/steps/switch.inline.mdwn

@@ -14,6 +14,7 @@ the rest of the instructions afterwards, we recommend you either:
    [[!img inc/qrcodes/tails_boum_org_install_mac_clone.png class="mac-clone" link="no"]]
    [[!img inc/qrcodes/tails_boum_org_install_mac_dvd.png class="mac-dvd" link="no"]]
    [[!img inc/qrcodes/tails_boum_org_install_debian_clone.png class="debian-clone" link="no"]]
+   [[!img inc/qrcodes/tails_boum_org_install_expert_usb.png class="expert-usb" link="no"]]
    [[!img inc/qrcodes/tails_boum_org_install_linux_usb.png class="linux-usb" link="no"]]
    [[!img inc/qrcodes/tails_boum_org_install_linux_clone.png class="linux-clone" link="no"]]
 
@@ -27,5 +28,6 @@ the rest of the instructions afterwards, we recommend you either:
      <a class="mac-clone" href="https://tails.boum.org/install/mac/clone/">https://tails.boum.org/install/mac/clone/</a>
      <a class="mac-dvd" href="https://tails.boum.org/install/mac/dvd/">https://tails.boum.org/install/mac/dvd/</a>
      <a class="debian-clone" href="https://tails.boum.org/install/debian/clone/">https://tails.boum.org/install/debian/clone/</a>
+     <a class="expert-usb" href="https://tails.boum.org/install/expert/usb/">https://tails.boum.org/install/expert/usb/</a>
      <a class="linux-usb" href="https://tails.boum.org/install/linux/usb/">https://tails.boum.org/install/linux/usb/</a>
      <a class="linux-clone" href="https://tails.boum.org/install/linux/clone/">https://tails.boum.org/install/linux/clone/</a>