Add Patreon bar

docs/_sass/footer.sass

@@ -24,6 +24,7 @@
   display: flex
   flex-wrap: wrap
   justify-content: flex-start
+  max-width: 400px
   > iframe,
   > a,
   > form,
@@ -44,6 +45,8 @@
     align-items: center
     display: flex
     width: 130px
+  .bd-patreon-button
+    margin-right: 0.5rem
 
 #newsletter
   .input

docs/_sass/patreon.sass

@@ -0,0 +1,24 @@
+.bd-patreon
+  align-items: center
+  background-color: $patreon-blue
+  color: $white
+  display: flex
+  justify-content: center
+  padding: 0.5rem 1rem
+  strong
+    color: currentColor
+
+.bd-patreon-text
+  font-size: $size-small
+  line-height: 1.25
+  margin-right: 0.5rem
+
+.bd-patreon-button
+  display: inline-block
+  flex-shrink: 0
+  height: 30px
+  width: 128px
+
++from(480px)
+  .bd-patreon-text
+    margin-right: 1rem