set footer to stick to the bottom of the page

src/styles/main.css

@@ -33,6 +33,7 @@
 
 html {
     font-size: 10px;
+    height: 100%;
 }
 
 * {
@@ -50,6 +51,7 @@ body {
   display: flex;
   flex-flow: column nowrap;
   justify-content: space-between;
+  min-height: 100%;
   padding: 2rem;
   width: 100%;
 }
@@ -75,6 +77,20 @@ body {
   width: 100%;
   align-items: center;
   justify-content: space-between;
+  flex-shrink: 0;
+  flex-grow: 0;
+}
+
+.page-content {
+    padding: 2rem;
+    flex-grow:1;
+}
+
+.site-footer {
+  flex-shrink: 0;
+  flex-grow:0;
+  width: 100%;
+  text-align:center;
 }
 
 .site-navigation ul {