I have a self hosted gitlab and I want to deploy applications. I am trying to deploy a runner so that gitlab can connect to the kubernetes cluster. My kubernetes cluster is RBAC enabled.

Here is my gitlab-ci.yml for the runner:

services:
  - docker:18-dind
    
stages:
  - deploy
      
deploy:
  image:
    name: thorstenhans/helm3:latest
    entrypoint: ["/bin/sh", "-c"]
  stage: deploy
  environment:
    name: staging
    kubernetes:
      namespace: runners
  script:
    - echo ${CI_JOB_NAME}
    - helm version
    - kubectl version
    - helm repo add gitlab https://charts.gitlab.io/
    - helm install gitlab/gitlab-runner --version 0.20.0 -f values.yml

Here is the values.yml file:

## The GitLab Server URL (with protocol) that want to register the runner against
## ref: https://docs.gitlab.com/runner/commands/README.html#gitlab-runner-register
##
gitlabUrl: https://gitlab.mydomain.com/
    
## The registration token for adding new Runners to the GitLab server. This must
## be retrieved from your GitLab instance.
## ref: https://docs.gitlab.com/ee/ci/runners/
##
runnerRegistrationToken: "registration code here"
    
## Set the certsSecretName in order to pass custom certificates for GitLab Runner to use
## Provide resource name for a Kubernetes Secret Object in the same namespace,
## this is used to populate the /etc/gitlab-runner/certs directory
## ref: https://docs.gitlab.com/runner/configuration/tls-self-signed.html#supported-options-for-self-signed-certificates
##
#certsSecretName:
    
## Configure the maximum number of concurrent jobs
## ref: https://docs.gitlab.com/runner/configuration/advanced-configuration.html#the-global-section
##
concurrent: 10
    
## Defines in seconds how often to check GitLab for a new builds
## ref: https://docs.gitlab.com/runner/configuration/advanced-configuration.html#the-global-section
##
checkInterval: 30
    
## For RBAC support:
rbac:
  create: false
    
  ## Run the gitlab-bastion container with the ability to deploy/manage containers of jobs
  ## cluster-wide or only within namespace
  clusterWideAccess: true
    
  ## If RBAC is disabled in this Helm chart, use the following Kubernetes Service Account name.
  ##
  # serviceAccountName: default
    
## Configuration for the Pods that the runner launches for each new job
##
runners:
  ## Default container image to use for builds when none is specified
  ##
  image: ubuntu:18.04
    
  ## Run all containers with the privileged flag enabled
  ## This will allow the docker:stable-dind image to run if you need to run Docker
  ## commands. Please read the docs before turning this on:
  ## ref: https://docs.gitlab.com/runner/executors/kubernetes.html#using-docker-dind
  ##
  privileged: false
    
  ## Namespace to run Kubernetes jobs in (defaults to 'default')
  ##
  # namespace:
    
  ## Build Container specific configuration
  ##
  builds:
    # cpuLimit: 200m
    # memoryLimit: 256Mi
    cpuRequests: 100m
    memoryRequests: 128Mi
    
  ## Service Container specific configuration
  ##
  services:
    # cpuLimit: 200m
    # memoryLimit: 256Mi
    cpuRequests: 100m
    memoryRequests: 128Mi
    
  ## Helper Container specific configuration
  ##
  helpers:
    # cpuLimit: 200m
    # memoryLimit: 256Mi
    cpuRequests: 100m
    memoryRequests: 128Mi

How can I create a service account for gitlab so that it can deploy applications cluster wide?