fix metallb matchlabels to be valid

[deitch]

fixes #247
cc @displague @enkelprifti98

[displague]

Let's add an example to https://github.com/equinix/cloud-provider-equinix-metal#metallb

CCM itself does not deploy the load-balancer or any part of it, including the ConfigMap. It only modifies an existing ConfigMap. This can be deployed by the administrator separately, using the manifest provided in the releases page, or in any other manner.

After that block, maybe something like this:

The CCM modifies the MetalLB ConfigMap rules (any more details we can add?) and uses special node-selectors. These node-selectors are ignored by MetalLB but are critical to the CCM management of MetalLB configuration. For example (perhaps we can make this look more practical):

- my-asn: 65000
  peer-asn: 65530
  peer-address: 169.254.255.1
  peer-port: 0
  source-address: 10.68.190.5
  hold-time: ""
  router-id: ""
  node-selectors:
  - match-labels:
      kubernetes.io/hostname: dc-worker-1
  - match-labels:
      nomatch.metal.equinix.com/service-namespace: default
      nomatch.metal.equinix.com/service-name: nginx-deployment
 - match-labels:
      nomatch.metal.equinix.com/service-namespace: ai
      nomatch.metal.equinix.com/service-name: trainer
 - match-labels:
      nomatch.metal.equinix.com/service-namespace: database
      nomatch.metal.equinix.com/service-name: mysql1

[deitch]

Updated the README. Ready for another look @displague