refactor(docs-infra): rename namespaced scss to index files (#41129)

scss files were forwarded from files that were named without convention, changes these file names to follow conventions

PR Close #41129

aio/src/styles/1-layouts/_index.scss

@@ -2,9 +2,9 @@
    LAYOUT STYLES
    ============================== */
 
-@import 'content-layout';
-@import 'doc-viewer';
-@import 'footer';
+@import 'content-layout/content-layout';
+@import 'doc-viewer/doc-viewer';
+@import 'footer/footer';
 @import 'layout-global';
 @import 'marketing-layout/marketing-layout';
 @import 'not-found';

aio/src/styles/main.scss

@@ -8,9 +8,9 @@
 @import './mixins';
 
 // import directories
-@import './0-base/base-dir';
-@import './1-layouts/layouts-dir';
-@import './2-modules/modules-dir';
+@import './0-base';
+@import './1-layouts';
+@import './2-modules';
 
 // import print styles
 @import './print';