add localization for subscribe button

i18n/en.toml

@@ -175,6 +175,9 @@ other = "Objectives"
 [prerequisites_heading]
 other = "Before you begin"
 
+[subscribe_button]
+other = "Subscribe"
+
 [ui_search_placeholder]
 other = "Search"
 

layouts/index.html

@@ -28,7 +28,7 @@
         	<input type="email" value="" name="EMAIL" class="email" id="mce-EMAIL" placeholder="{{ T "input_placeholder_email_address" }}" aria-label="email" required>
             <!-- real people should not fill this in and expect good things - do not remove this or risk form bot signups-->
             <div style="position: absolute; left: -5000px;" aria-hidden="true"><input type="text" name="b_3885586f8f1175194017967d6_11c1b8bcb2" tabindex="-1" value=""></div>
-            <div class="clear"><input type="submit" value="Subscribe" name="subscribe" id="mc-embedded-subscribe" class="button"></div>
+            <div class="clear"><input type="submit" value="{{ T "subscribe_button" }}" name="subscribe" id="mc-embedded-subscribe" class="button"></div>
             </div>
         </form>
         <h5 style="text-align: center"><a href="https://us10.campaign-archive.com/home/?u=3885586f8f1175194017967d6&id=11c1b8bcb2" aria-label="Kube Weekly" style="color: #3371E3; font-weight: 400; font-size: 20px">{{ T "main_kubeweekly_past_link" }}</a></h5>