Update documentation issue request template

[jmikell821]

Description

Revise the doc issue request template to include new requirements surrounding Serverless, dev release process, etc.

What needs to be included in the template:

Description
Describe what needs to be documented. Please provide all necessary user details.

Resources
Please include the relative pull request(s) or issue(s).

Which documentation set does this change impact?
Serverless only, ESS only, Serverless and ESS, Unknown.

Feature differences
If you selected Serverless and ESS above, please describe any feature difference between each platform.

When is the feature expected to be released?
Please include the Stack release version and/or Serverless public release date.

Acceptance test criteria
List all the ATC of each action and its intended result. For example: As a user, when [action (e.g., viewing, clicking, selecting, etc.)] I should [insert the expected result].

Prerequisites and privileges
Are there any required role privileges or subscription level tiers?

Test environment
Please include the environment which the docs team can test this feature. Example: https://kibana.siem.estc.dev/. If one isn't available, please list the steps to generate data we can test.

Feature flag limitations
Are there any feature flags that need to be enabled?

Point of contact
Please assign at least one point of contact. Add as many stakeholders as needed -- such as those from dev, design, product management, etc.

[joepeeples]

I think we can close this now that #4308 is merged, but @jmikell821 I'll let you make the final call.

[jmikell821]

Merged #4308.