Fixes #53 - Added detection and install links for iOS safari

includes/index.tmpl

Index: includes/index.tmpl
===================================================================
--- a/includes/index.tmpl
+++ b/includes/index.tmpl
@@ -70,16 +70,17 @@
 
     <div id="install">
       <a class="install-button" href="https://update.adblockplus.org/latest/adblockplusfirefox.xpi" id="install-firefox">{{"Agree and Install for Firefox"|translate("s13")}}</a>
       <a class="install-button" href="https://chrome.google.com/webstore/detail/cfhdojbkjhnklbpkdaibdccddilifddb" id="install-chrome" onclick="chrome.webstore.install(); return false;">{{"Agree and Install for Chrome"|translate("s14")}}</a>
       <a class="install-button" href="https://addons.opera.com/extensions/details/opera-adblock/?display=en-US" id="install-opera">{{"Agree and Install for Opera"|translate("s15")}}</a>
       <a class="install-button" href="android-install" id="install-android">{{"Agree and Install for Android"|translate("s16")}}</a>
       <a class="install-button" href="https://update.adblockplus.org/latest/adblockplusie.exe" id="install-internet-explorer">{{"Agree and Install for Internet Explorer"|translate("s17")}}</a>
       <a class="install-button" href="https://update.adblockplus.org/latest/adblockplussafari.safariextz" id="install-safari">{{"Agree and Install for Safari"|translate("s18")}}</a>
+      <a class="install-button" href="https://itunes.apple.com/us/app/adblock-plus-abp-remove-ads-browse-faster-without-tracking/id1028871868?mt=8" id="install-ios">{{"Agree and Install for Safari"|translate("s18")}}</a>

[ire, 2018/04/12 14:30:32]

Suggestion/Question: Since this string is identical to the one above, is there a
way to output the same string by referencing the ID without repeating the string
itself?

[juliandoucette, 2018/04/12 15:02:23]

~Yes. But it's not pretty in .tmpl format. It looks like {{ "" |
translate("s18") }}.

I'd prefer to leave it as-is for now.

[ire, 2018/04/12 15:13:50]

Ah okay, that's fine. 

       <a class="install-button" href="https://chrome.google.com/webstore/detail/cfhdojbkjhnklbpkdaibdccddilifddb" id="install-yandex-browser" onclick="chrome.webstore.install(); return false;">{{"Agree and Install for Yandex Browser"|translate("s19")}}</a>
       <a class="install-button" href="https://www.microsoft.com/store/p/adblock-plus/9nblggh4r9nz" id="install-edge">{{"Agree and Install for Microsoft Edge"|translate("install-edge")}}</a>
     </div>
 
     <div id="other-platform">
         <div>{{"Download Adblock Plus for another platform"|translate("other-platform")}}</div>
         <ul>
           <li>