Feature: Added post sharing options.

Also added a license statement at the bottom of the posts.

assets/css/_dark/dark-main.scss

@@ -45,6 +45,7 @@
   --tb-odd-bg: rgba(52, 53, 42, 0.52); /* odd rows of the posts' table */
   --tb-even-bg: rgb(31, 31, 34); /* even rows of the posts' table */
   --footnote-target-bg: rgb(63, 81, 181);
+  --btn-sharing: #6c757d;
 
   hr {
     border-color: var(--main-border);