Added webpack-ignore for source-map-support warning (fixes #556)

[svenefftinge]

No description provided.

[akosyakov]

There is already an explicit dependency to it: https://github.com/theia-ide/theia/blob/c20dab0009b0c4a10f3c97115edba370615a8255/dev-packages/cli/package.json#L50

[svenefftinge]

that's the wrong version. Using strictly 0.4.3 removed the warning. OTOH we could ignore the warning. Looking at the actual code, it seems to be expected for webpack:

 try {
      Module = require('module');
    } catch (err) {
      // NOP: Loading in catch block to convert webpack error to warning.
    }