Add the ability to use Username/Password as authentication method

[traviskosarek]

The task currently authenticates to a Git repository by using a PAT token. Adding in an option to authenticate via a Username/Password would expand the options for users to interact with their Git repositories and provide a more robust experience.

As discovered in issue #6 , there may be an underlying issue outside of the task that restricts users to authenticating via a username/password instead of a PAT token. While a workaround exists by putting the "username:password" in the PAT token field, this is not ideal because of the mismatch of label and value within the task.

[calebcartwright]

Btw @traviskosarek looking back at this (a few years on 😄), is there any reason this couldn't be sufficiently resolved by just renaming the input names and labels on the input (to cover both yaml and visual designer pipelines) with some accompanying minor enhancements to documentation?