Merge branch 'calculator' into tmp_2020calc

- Fix some missing alt attributes & {% trans %} tags

tool/template-learn-history.html

@@ -36,7 +36,7 @@
         <h2 class="h1 text-center mx-auto mb-20">{% trans %}Timeline of XRP Evolution{% endtrans %}</h2>
         <div class="col-lg-10 offset-lg-1">
           <div class="timeline">
-            <div class="timeline-block">
+            <div class="timeline-block mb-10">
               <div class="timeline-dot"></div>
               <div class="timeline-content">
                 <h4 class="mb-10">{% trans %}2011 XRP Ledger Development{% endtrans %}</h4>
@@ -44,7 +44,7 @@
                 <p>{% trans %}Their initial observations about the high energy consumption and scalability issues that would plague Bitcoin proved prescient. (In 2019, estimates suggest Bitcoin mining used more energy than the entire country of Portugal!) Moreover, their initial read indicated that significant problems could arise if any miner obtained (or miners colluded to obtain) greater than 50% of the mining power—that risk persists with Bitcoin (and Ethereum) today as mining power has consolidated in China.{% endtrans %}</p>
               </div>
             </div>
-            <div class="timeline-block">
+            <div class="timeline-block mb-10">
               <div class="timeline-dot"></div>
               <div class="timeline-content">
                 <h4 class="mb-10">{% trans %}2012 XRP Launched{% endtrans %}</h4>
@@ -59,7 +59,7 @@
                 <p>{% trans %}Chris Larsen was the CEO of OpenCoin, and at the company's founding, Jed was co-founder and CTO, David Schwartz was the Chief Cryptography Officer, and Arthur Britto an advisor.{% endtrans %}</p>
               </div>
             </div>
-            <div class="timeline-block">
+            <div class="timeline-block mb-10">
               <div class="timeline-dot"></div>
               <div class="timeline-content">
                 <h4 class="mb-10">{% trans %}2013 OpenCoin Rebranded to Ripple Labs{% endtrans %}</h4>
@@ -74,7 +74,7 @@
 
       <section class="row mt-30 mb-40">
         <h6 class="section-marker" id="section-marker-podcast">{% trans %}Podcast{% endtrans %}</h6>
-        <div class="col-sm-5 order-1 order-sm-2 mb-10">
+        <div class="col-sm-5 order-1 order-sm-2 mb-10 text-center">
           <img class="mw-100" src="./img/graphics/chris-larsen.png">
         </div>
         <div class="col-sm-5 offset-sm-1 order-2 order-sm-1 mt-20">