feat: Color Themes - Header + Sidebar + Footer support

server/views/common/footer.pug

@@ -1,4 +1,4 @@
-footer.footer
+footer.footer(class=['is-' + appconfig.theme.footer])
   span
     = t('footer.poweredby') + ' '
     a(href='https://github.com/Requarks/wiki') Wiki.js

server/views/common/header.pug

@@ -1,6 +1,6 @@
 
 #header-container
-  nav.nav#header
+  nav.nav#header(class=['is-' + appconfig.theme.primary])
     .nav-left
       block rootNavLeft
         a.nav-item(href='/')