adding simple alt attributes to imgs on ev3 landing page

src/views/ev3/ev3.jsx

@@ -31,7 +31,10 @@ class EV3 extends ExtensionLanding {
     render () {
         return (
             <div className="extension-landing ev3">
-                <ExtensionHeader imageSrc="/images/ev3/ev3-illustration.png">
+                <ExtensionHeader
+                    imageAlt={this.props.intl.formatMessage({id: 'ev3.imgAltEv3illustration'})}
+                    imageSrc="/images/ev3/ev3-illustration.png"
+                >
                     <FlexRow className="column extension-copy">
                         <h2><img src="/images/ev3/ev3.svg" />LEGO MINDSTORMS EV3</h2>
                         <FormattedMessage
@@ -119,13 +122,19 @@ class EV3 extends ExtensionLanding {
                             <Steps>
                                 <Step>
                                     <div className="step-image">
-                                        <img src="/images/ev3/ev3-accept-connection.png" />
+                                        <img
+                                            alt={this.props.intl.formatMessage({id: 'ev3.imgAltAcceptConnection'})}
+                                            src="/images/ev3/ev3-accept-connection.png"
+                                        />
                                     </div>
                                     <p><FormattedMessage id="ev3.acceptConnection" /></p>
                                 </Step>
                                 <Step>
                                     <div className="step-image">
-                                        <img src="/images/ev3/ev3-pin.png" />
+                                        <img
+                                            alt={this.props.intl.formatMessage({id: 'ev3.imgAltAcceptPasscode'})}
+                                            src="/images/ev3/ev3-pin.png"
+                                        />
                                     </div>
                                     <p><FormattedMessage id="ev3.acceptPasscode" /></p>
                                 </Step>
@@ -170,7 +179,10 @@ class EV3 extends ExtensionLanding {
                                 />
                             </span>
                             <div className="step-image">
-                                <img src="/images/ev3/ev3-motor-port-a.png" />
+                                <img
+                                    alt={this.props.intl.formatMessage({id: 'ev3.imgAltPlugInMotor'})}
+                                    src="/images/ev3/ev3-motor-port-a.png"
+                                />
                             </div>
                         </Step>
                         <Step

src/views/ev3/l10n.json

@@ -34,5 +34,12 @@
     "ev3.otherComputerConnectedText": "Only one computer can be connected to an EV3 at a time. If you have another computer connected to your EV3, disconnect the EV3 or close Scratch on that computer and try again.",
     "ev3.updateFirmwareTitle": "Try updating your EV3 firmware",
     "ev3.updateFirmwareText": "We recommend updating to EV3 firmware version 1.10E or above. See {firmwareUpdateLink}. We recommend following the instructions for \"Manual Firmware Update\".",
-    "ev3.firmwareUpdateText": "firmware update instructions from LEGO"
+    "ev3.firmwareUpdateText": "firmware update instructions from LEGO",
+    "ev3.imgAltEv3illustration": "Illustration of an EV3 Computer featuring some examples of interacting with an EV3.",
+    "ev3.imgAltAddExtension": "In the editor, click on the \"Add Extensions\" button on the lower left.",
+    "ev3.imgAltAcceptConnection": "Use the buttons of your EV3 to accept the connection.",
+    "ev3.imgAltAcceptPasscode": "Use the center button of your EV3 to accept the passcode.",
+    "ev3.imgAltWaitForWindows": "Windows notifies you when EV3 is ready.",
+    "ev3.imgAltEnterPasscodeMac": "Enter the passcode into the connection request window opening on your Mac.",
+    "ev3.imgAltPlugInMotor": "Port A is not to be confused with Port 4 on the other side of the EV3."
 }