Create a Marketplace publisher and get a personal access token

[lou1306]

Links:

• https://code.visualstudio.com/api/working-with-extensions/publishing-extension#create-a-publisher
• https://code.visualstudio.com/api/working-with-extensions/publishing-extension#get-a-personal-access-token

After getting a PAT, we should take measure to keep it private. A good solution would be to add it as a "repository secret" (Settings > Secrets and variables > Actions) and only interact with it through GitHub Actions.

Once we have a publisher, we can add its identifier to package.json.