Update JIRA documentation

[joshfalgout]

Customer complained that our Jira docs are lacking

Update the JIRA integration page to clearly describe each field and the reason for using those fields.

Add instructions for creating an API user and token based auth if applicable.

Prisma Cloud has great docs we can use as examples: https://docs.paloaltonetworks.com/prisma/prisma-cloud/prisma-cloud-admin/configure-external-integrations-on-prisma-cloud/integrate-prisma-cloud-with-jira