Add link for radar viewer

[partly-igor]

Description

As described in #1648 we'd like to add a link to the radar viewer so that users who are interested can more radar details. In #1648 @greg-does-weather noted that we should be able to pull the users location when sending the user to the radar viewer

Documenting here for posterity, the URL parameter is called settings, and is v1_{ base64-encoded JSON string}.

The JSON object looks like this:

{
  agenda: {
    id: 'weather',
    center: [ -92.37, 44.64 ],
    location: [ -100.405, 41.424 ],
    zoom: 7.839999999999999,
    layer: 'bref_qcd'
  },
  animating: false,
  base: 'standard',
  artcc: false,
  county: false,
  cwa: false,
  rfc: false,
  state: false,
  menu: true,
  shortFusedOnly: false,
  opacity: {
    alerts: 0.8,
    local: 0.6,
    localStations: 0.8,
    national: 0.6 }
}

Getting the right settings string would be ?settings=v1_${ btoa(JSON.stringify(obj)) }

Figma documentation

Designs/Context

Acceptance Criteria

• Add a link to the radar viewer
• Link should be based on the users' location and show the correct geography once they open up the radar viewer
• Implementation follows the designs

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