docs: mention Prometheus in intro

[StackScribe]

@agardnerIT commented:

Nitpicking but: Datadog, Dynatrace, Lightstep, Honeycomb, Splunk

1. missing Prometheus
2. it should be alphabetical OR we are subtly suggesting that datadog is better than DT.
3. (My opinion) but we shouldn’t give free promotion. If the vendors want their name listed here, they should write a provider. By giving this list, we’re putting Honeycomb on the same footing at DT.

This PR:

• Adds Prometheus to the list of data providers and arranges them in the order they were implemented for KLT
• Replaced the names of other data providers with "and others"
• Tweaked the prose a bit for better flow

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
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0 Code Smells

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[StackScribe]

The build error is about the link to the HPA docs. The link works fine -- I think markdownlint has a bit of trouble to xrefs to subsections of a page