Pascal-case annotator-component SCSS modules

Leave class naming alone for now, as these modules haven't been fully
normalized/component-ized yet.

src/styles/annotator/annotator.scss

@@ -12,8 +12,8 @@
 @use '@hypothesis/frontend-shared/styles';
 
 // Annotator-specific components.
-@use './components/adder';
-@use './components/toolbar';
+@use './components/Adder';
+@use './components/Toolbar';
 @use './bucket-bar';
 @use './highlights';
 @use './notebook';