build(webpack): Fixed out directory to include `src` subfolder

[Aerex]

Context

Publishing failing using webpack due to the expected extension.js file not in the correct place.

Callouts

• Adding npm run clean to remove out directory to ensure we are in a clean state before building.

#

Steps to Test

1. Change directory to the root of the local repo
2. Run the command: ./node_modules/.bin/vsce package
3. Verify that the ibm-developer-0.1.0.vsix is built successfully
4. Open VSCode
5. Uninstall IBM Cloud CLI extension if it is installed
6. Close VSCode and reopen
   • Sometimes VSCode may still cache uninstall extension so it is best to reopen VSCode.
7. Reinstall the extension using the .vsix file built in step 3
8. Verify the extension is installed successfully
9. Run a few commands via the Command Palette to verify commands are still functional.