refactor: migrate some styling features to the new architecture

Again, by using StylesheetScript we also get dynamic styles for free.

Bug: twpowertools:176, twpowertools:61
Change-Id: I8c660f8b9cddaf56b3a29c8d07d48d070ee2cd34
diff --git a/src/features/stickySidebarHeaders/ui/styles.css b/src/features/stickySidebarHeaders/ui/styles.css
new file mode 100644
index 0000000..cd64b74
--- /dev/null
+++ b/src/features/stickySidebarHeaders/ui/styles.css
@@ -0,0 +1,6 @@
+material-drawer .main-header {
+  background: var(--TWPT-drawer-background, #fff) !important;
+  position: sticky;
+  top: 0;
+  z-index: 1;
+}