css: replace value by a pico variable

- Replaces a spacing value in the medias SCSS file by the pico variable.
- Fixes the IDs of the personal and professional contact headers, to
  ease linking.
- Rewrite the indentation of a shortcode.

Co-Authored-by: iGor milhit <igor@milhit.ch>

layouts/partials/perso.html

@@ -1,4 +1,4 @@
-<h2 id="contactsPriv">{{ i18n "contactsPriv" }}</h2>
+<h2 id="contacts-priv">{{ i18n "contactsPriv" }}</h2>
 <dl class="home-lists">
   {{ with .Site.Params.contactsPriv.email }}
     <dt>{{ i18n "e-mail" }}</dt>

layouts/partials/pro.html

@@ -1,4 +1,4 @@
-<h2 id="contactsPro">{{ i18n "contactsPro" }}</h2>
+<h2 id="contacts-pro">{{ i18n "contactsPro" }}</h2>
 <dl class="home-lists">
   {{ with .Site.Params.contactsPro.email }}
   <dt>{{ i18n "e-mail" }}</dt>