ui: Add theme from bootswatch

frontend/ui/src/components/Header.svelte

@@ -51,7 +51,8 @@
         <HeaderPartners />
     </Container>
 </div>
-<Navbar class="sticky-top" color="dark" dark expand="md">
+<div class="sticky-top">
+<Navbar color="dark" dark expand="md">
     <NavbarToggler on:click={() => (isOpen = !isOpen)} />
     <Collapse {isOpen} navbar expand="md" on:update={handleUpdate}>
         <Nav navbar>
@@ -103,6 +104,7 @@
     </Collapse>
 </Navbar>
 <Progress value={$time.progression * 100} color="info" style="height: 5px; border-radius: 0;" />
+</div>
 
 <style>
  .teamname {