Abstract out isAdmin check to new utility in /utils

[Asartea]

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1. Description of the Feature Request: We currently duplicate the code for checking if an user is an "admin" in a number of places using roughly this snippet[1]

      authorMember.roles.cache.forEach((value) => {
        if (config.roles.adminRolesName.includes(value.name)) {
          isAdmin = true;
        }
      });

this duplicates code, and also can be simplified to

const isAdmin = member.roles.cache.some((role) => roles.adminRolesName.includes(role.name))

It would be beneficial to abstract this functionality out to a new is-admin.js file in /utils

[1] Taken from points.js

2. Acceptance Criteria:

• [ ] There is an utility function which checks if an member is an admin
• [ ] All code that needs to check this uses the utility function