Tweak and re-organize ESLint config (#38369)

* Tweak and re-organize ESLint config

* merge individual configs to the root config
* enable more eslint-plugin-import rules
* lint markdown files

* Lint

js/tests/integration/bundle-modularity.js

@@ -1,3 +1,5 @@
+/* eslint-disable import/extensions, import/no-unassigned-import */
+
 import Tooltip from '../../dist/tooltip'
 import '../../dist/carousel'
 

js/tests/integration/rollup.bundle-modularity.js

@@ -1,7 +1,7 @@
-/* eslint-env node */
+'use strict'
 
 const commonjs = require('@rollup/plugin-commonjs')
-const configRollup = require('./rollup.bundle')
+const configRollup = require('./rollup.bundle.js')
 
 const config = {
   ...configRollup,

js/tests/integration/rollup.bundle.js

@@ -1,4 +1,4 @@
-/* eslint-env node */
+'use strict'
 
 const { babel } = require('@rollup/plugin-babel')
 const { nodeResolve } = require('@rollup/plugin-node-resolve')