fix(extensions): change portable extensions dir

[LuisUrrutia]

Short description of what this resolves:

Solves the issue shanalikhan#756 caused by a hardcoded extension dir.
This is a temporary workaround and we should use the env variables to check a valid extension dir instead of hardcoded ones:

Changes proposed in this pull request:

• The extensionDir variable was changed to .vscode/ to prevent the sync of "something" with .vscode in its name. (ex: bung87.vscode-gemfile)
  

  code-settings-sync/src/service/pluginService.ts

  Line 12 in 3646117

  const extensionDir: string = ".vscode";

• The extensionDirPortable variable was changed to /extensions/ because the path for the extensions folder in a portable VSCode instance, is extensions
  

  code-settings-sync/src/service/pluginService.ts

  Line 13 in 3646117

  const extensionDirPortable: string = "/data/extensions/";

  
  Ref to extensions path in vscode:
  https://github.com/Microsoft/vscode/blob/14f25a610224cea1b7fc97da63ad2304951f60a5/src/vs/platform/environment/node/environmentService.ts#L168

Fixes: shanalikhan#756

How Has This Been Tested?

The extension was "installed" in a portable vscode and executed to sync the settings. It works nicely.

Checklist:

• I have read the contribution guidelines.
• My change requires a change to the documentation and Github Wiki.
• I have updated the documentation and Wiki accordingly.

[chase9]

Hello Luis,

Thank you for your PR. However, since this is a fork, you're probably going to want to submit your PR to the main project at https://github.com/shanalikhan/code-settings-sync so that everyone can benefit from your work. Otherwise, I'd have to fast-forward and submit a PR of my own.

Let me know if you need any help doing this.

Chase