docs: Detect secrets drift (graph-links) example topic does not match included image

[polarathene]

Expected Behavior

Image example should align with the prior config and command covered by the section.

Current Behavior

The current section of the README details tracking drift between two separate ENV file sources where the key has changed. It discusses "wiring" them together, but then depicts an image showing something else entirely (although a similar MailGun ENV is shown):

https://github.com/tellerops/teller#beetle-detect-secrets-and-value-drift-graph-links-between-providers

Possible Solution

The section could it be updated with an image to better reflect what the rest of the section was explaining?

Steps to Reproduce

1. Read the README section (screenshot shown above)
2. Notice that the provided image is not related to the example config + command.

Context

The README is a tad confusing to glance over as someone looking into what the project can do, especially with managing ENV without secrets providers in the mix (just keeping it simple with dotenv or similar).

This wasn't the only section that seemed a tad off, and I was left with the impression that I'd need to get the binary and play around to fill in the gaps.

The README "docs" jump into env / env_sync keys early on, but don't really touch on it earlier. It seems that each provider is documented with slightly different usage for it, but the two keys presumably have a generic functionality / purpose that could be clarified earlier? (EDIT: I somehow missed this overview which does explain env + env_sync, it was just inline docs looking similar to other snippets which might be why I didn't pick up on it the first few times)

There's presently one big kitchen-sink style example, but it'd be nice to have some of the examples spread over the README covered in an examples/ folder, perhaps using dotenv / process_env providers to showcase the features / usage of teller, and then separately focus on the broader offering of providers supported and their config differences?

Specifications

• Content was introduced in this PR https://github.com/tellerops/teller/pull/16/files#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5R207-R232
• Image seems to have been from discussion of the feature that led to the PR: How would you suggest setting secrets? #15 (comment)