Create dedicated page for roles.

[ep-93]

User Story

Confusion about the roles that the platform has and what they do occurs often, so by defining each role and also the process a user needs to take in requesting a new one, we will hopefully reduce any role duplication.

We have agreed on sticking to the current method, however creating a page for roles, and having role creation and links to our roles is a minimum.

Value

Having defined roles and a process on our docs will help users understand it.

Definition of done

• [ ] Page has been created
• [ ] Role creation process has been defined
• [ ] Each role is defined with links to code

Reference

https://github.com/ministryofjustice/modernisation-platform/issues/4184