Update contributing.md to specify the Changelog.md format

[zFernand0]

If this (i.e. using past-tense in changelog.md) is a standard it should be documented in contributing.md. if it is, it's fine to link it

Originally posted by @dkelosky in zowe/imperative#721 (comment)

[t1m0thyj]

This is mentioned in CONTRIBUTING.md in the Zowe CLI repo:

Start the sentence with a verb in past tense. For example "Added...", "Improved...", "Enhanced...".

Admittedly this info is kind of hard to find, since I don't believe other repos like Imperative link mention this in their CONTRIBUTING.md. Maybe they should link to the file in the Zowe CLI repo?

[dkelosky]

I'd argue that the info isn't hard to find; rather, I thought they were unconnected. If they are linked, it would be great to know which sections (I assume not all) of Zowe CLI CONTRIBUTING.md apply to imperative's CONTRIBUTING.md.

Thanks!

[zFernand0]

Since it's documented already in the Readme, should we close this issue.
Or do we want to re-use it to implement a PR Template that reminds people of a few key items (like the past tense in the changelogs) when they open a PR.

[dkelosky]

Can you clarify what s already documented in the README? I was mentioning that there is a Zowe CLI CONTRIBUTING.md and an Imperative CONTRIBUTING.md. It looks like only the Zowe CLI version mentions past tense. Thanks!

[zFernand0]

After combining Imperative into the CLI, I believe we've also consolidated the contributing.md files.
So, the imperative contributing.md shouldn't be referenced since the repo is now a public archive 😋
https://github.com/zowe/imperative/blob/master/CONTRIBUTING.md#changelog-update-guidelines