Fix tap's documentation to make clear the differences from the original tap and how to install it. - [merged]

[MeltyBot]

Merges 7-fix-documentation-on-how-to-install-meltano-version-of-tap-salesforce -> master

Migrated from GitLab: https://gitlab.com/meltano/tap-salesforce/-/merge_requests/7

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Fix tap's documentation to make clear the differences from the original tap and how to install it:

1. Add differences between the two taps
2. Add installation instructions on how to install the Meltano maintained version of the tap
3. Add clear link to the original Tap in case people want to use that
4. Add clear instruction on the different configuration options

Closes #7