Update ws requirement from ^5.2.0 to ^7.0.0

[dependabot-preview]

Updates the requirements on ws to permit the latest version.

Release notes

Sourced from ws's releases.

7.0.0

Breaking changes

• Dropped support for Node.js 6 (1e6999bb).
• Dropped support for url.Url instances in the WebSocket constructor
  (692d7b47).
• The behavior of WebSocket#{p{i,o}ng,send}() has changed when the
  readyState attribute is not OPEN (#1532)
  • If the readyState attribute is CONNECTING, an exception is thrown.
  • If the readyState attribute is CLOSING or CLOSED
    • The bufferedAmount attribute is increased by the length of the data
      argument in bytes.
    • If provided, the callback function is called with an error.
    • No exception is thrown even if the callback function is not provided.

Commits

• 092a822 [dist] 7.0.0
• 1b85466 [minor] Use crypto.randomFillSync() to generate the masking key
• 993b0cd [minor] Make extension.parse() use null-prototype objects
• aca3858 [example] Clean up examples
• 4a9a773 [example] Rename serverstats to server-stats
• 3eff077 [example] Remove unmaintained fileapi example
• 379def6 [lint] enable no-var rule
• 01bb91d [ci] Test on node 12
• 6824e8c [minor] Use Reflect.apply()
• ddf0aca [minor] Use object spread syntax instead of Object.assign()
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #35.