fix: respect colors dict in metropolis theme (#133)

Author: ParaN3xus

themes/metropolis.typ

@@ -174,15 +174,15 @@
     stack(
       dir: ttb,
       spacing: 1em,
-      utils.display-current-heading(level: level, numbered: numbered),
+      text(self.colors.neutral-darkest, utils.display-current-heading(level: level, numbered: numbered)),
       block(
         height: 2pt,
         width: 100%,
         spacing: 0pt,
         components.progress-bar(height: 2pt, self.colors.primary, self.colors.primary-light),
       ),
     )
-    body
+    text(self.colors.neutral-dark, body)
   }
   self = utils.merge-dicts(
     self,