allow to use PGP key for IndieAuth

https://indieauth.com/pgp

exampleSite/config.toml

@@ -53,6 +53,7 @@ theme = "hyde-hyde"
     telegram = "<username>"
     email = "your-email@example.com"
     # gravatar = "your-email@example.com"
+    # pgpkey = "<path-to-your-key-in-/static>"
 
 ## Main Menu
 [[menu.main]]

layouts/partials/sidebar/social.html

@@ -45,4 +45,7 @@
 	{{ with .Site.Params.social.email }}
 	<a href="mailto:{{.}}" rel="me"><i class="fas fa-at fa-lg" aria-hidden="true"></i></a>
 	{{ end }}
+	{{ with .Site.Params.social.pgpkey }}
+	<a href="{{.}}" rel="pgpkey"><i class="fa fa-key fa-lg" aria-hidden="true"></i></a>
+	{{ end }}
 </section>