fix(head.html): Adds robustness to config.yaml favicon definitions

Initially assumed that `href` definitions should have `/...` as their
pattern, and `baseURL` would always end with `/`, however the omission
of `/` as the prefix of the former and suffix of the latter
simultaneously, would result in broken favicon paths. Final comment:
`..///...` is not breaking, which is worst case scenario with this fix.

layouts/partials/head.html

@@ -18,7 +18,7 @@
   {{ $favicon | safeHTML }}
   {{ else }}
   {{ range $favicon }}
-  <link rel="{{.rel}}" {{if .type}}type="{{.type}}"{{end}} {{if .sizes}}sizes="{{.sizes}}"{{end}} href="{{$.Site.BaseURL}}{{.href}}" />
+  <link rel="{{.rel}}" {{if .type}}type="{{.type}}"{{end}} {{if .sizes}}sizes="{{.sizes}}"{{end}} href="{{$.Site.BaseURL}}/{{.href}}" />
   {{- end }}
   {{ end }}