chore: upgrade eslint (last 5.x version), eslint-config-standard, eslint-plugin-node

eslint 6.x seems to be incompatible, because each eslint element needs to have the same eslint version configured

webpack.common.js had to be adjusted for new eslint rule

package.json

@@ -64,10 +64,10 @@
     "clean-webpack-plugin": "^1.0.1",
     "cross-env": "^5.1.3",
     "cz-conventional-changelog": "^3.0.0",
-    "eslint": "^5.15.3",
-    "eslint-config-standard": "^12.0.0",
+    "eslint": "^5.16.0",
+    "eslint-config-standard": "^13.0.1",
     "eslint-plugin-import": "^2.16.0",
-    "eslint-plugin-node": "^8.0.0",
+    "eslint-plugin-node": "^9.1.0",
     "eslint-plugin-promise": "^4.0.1",
     "eslint-plugin-standard": "^4.0.0",
     "html-webpack-plugin": "^3.2.0",

webpack.common.js

@@ -4,8 +4,8 @@ var webpack = require('webpack')
 
 module.exports = {
     entry: {
-        'opensheetmusicdisplay': './src/index.ts', // Main index (OpenSheetMusicDisplay and other classes)
-        'demo': './demo/index.js' // Demo index
+        opensheetmusicdisplay: './src/index.ts', // Main index (OpenSheetMusicDisplay and other classes)
+        demo: './demo/index.js' // Demo index
     },
     output: {
         path: path.resolve(__dirname, 'build'),