Dynamic instead of hard-coded dev main entry

[alfrededison]

• Version: ^2.8.2

• Target:

Currently, out/dev/dev-runner.js use hard-coded path to main entry to start electron in dev

args.push(path.join(projectDir, "dist/main/main.js"));

We should use dynamic path instead, like

args.push(path.join(electronWebpackConfig.commonDistDirectory, "main", "main.js"));