sophisticated rollup setup and eslint base setup

packages/overlayscrollbars-jquery/src/dir/abc.js

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+export default 'abc';

packages/overlayscrollbars-jquery/src/file.js

@@ -0,0 +1,4 @@
+const a = 1 + 1;
+export default {
+  a,
+};

packages/overlayscrollbars-jquery/src/index.js

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+import abc from 'dir/abc';
+import not from 'dir/not.png';
+import file from 'file';
+import j from 'jquery';
+import { a, b, c } from 'test';
+
+export default j('div');
+export { a, b, c, file, abc, not };

packages/overlayscrollbars-jquery/src/test.js

@@ -0,0 +1,3 @@
+export const a = 'a';
+export const b = 'b';
+export const c = 'c';