SOLIDPOD: Allow users to create a SolidPod template app from anywhere

[tonypioneer]

Description

Currently, users can generate a SolidPod template application by first cloning the SolidPod repository from GitHub and then running the following command within the project directory:

dart run solidpod:create my_pod_app

However, if the command is executed from a different directory, template generation fails with the following error:

Found no `pubspec.yaml` file in <folder> or parent directories.

In addition, if a template application is generated from an arbitrary location using:

flutter pub global activate solidpod
solidpod create my_pod_app

the generated application's pubspec.yaml file will be missing all third-party package dependencies that are normally included in the template project.

Closing Criteria

Checklist for closing the issue:

• No errors from make prep
• All tests pass make qtest
• Users can generate a SolidPod template app from any location
• The pubspec.yaml file is correct