Update .editorconfig

[szepeviktor]

Please consider adding a CI step:

    steps:
      - name: "Checkout"
        uses: "actions/checkout@v2.3.1"

      - name: "Install NodeJS"
        uses: "actions/setup-node@v2-beta"
        with:
          node-version: '12'

      - name: "Install eclint"
        working-directory: "./plugin-name"
        run: "npm install --no-package-lock eclint"

      - name: "Check EditorConfig adherence"
        working-directory: "./plugin-name"
        run: "npx eclint check"

It checks all files, more than PHPCS.