refactor: drop webpack@4 (#509)

BREAKING CHANGE: minimum supported `webpack` version is `5`

Author: cap-Bernardito

.github/workflows/nodejs.yml

@@ -56,7 +56,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
         node-version: [10.x, 12.x, 14.x]
-        webpack-version: [4, latest]
+        webpack-version: [latest]
 
     runs-on: ${{ matrix.os }}