Add johngmyers to reviewers

[johngmyers]

Description

Per the requirements in https://github.com/kubernetes/community/blob/master/community-membership.md :

[x] member for at least 3 months
[x] Primary reviewer for at least 5 PRs to the codebase

#3285, #3174, #3201, #3104, #3589,
#3590, #3295, #3263, #3297, #2553

[x] Reviewed or merged at least 20 substantial PRs to the codebase

#3285, #3174, #2157, #3261, #3201,
#3297, #2461, #3546, #3589, #3588,
#3590, #3607, #3600, #3603, #3590,
#3295, #3263, #3263, #3640, #3222,
#2054, #2553, #3104,

[x] Knowledgeable about the codebase
[ ] Sponsored by a subproject approver
[ ] With no objections from other approvers
[x] Done through PR to update the OWNERS file
[x] May either self-nominate, be nominated by an approver in this subproject, or be nominated by a robot

Checklist

• Unit tests updated
• End user documentation updated

[szuecs]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johngmyers, szuecs

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [szuecs]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[Raffo]

/lgtm