[Tools] Using Webpack require.context to conditionally load file

require.context: https://webpack.js.org/guides/dependency-management/#requirecontext

require.context(directory, useSubdirectories = true, regExp = /^./.*$/, mode = 'sync');

For example, we have a file for local env called: 'dev-tools.local.js', we want to load it if exists, but don't cause any error if file not exists. 

const requireDevToolsLocal = require.context(
    './', // look for current dir
    false, // don't look into sub-dir
    /dev-tools.local.js/ // regex filename
)
const localFile + requireDevToolsLocal.keys()[0];
// if localfile not exist, don't load the file
if (local) {
    requireDevToolsLocal(local)
}