[Snyk] Security upgrade socket.io from 2.4.1 to 3.0.0

[Danielv123]

This PR was automatically created by Snyk using the credentials of a real user.

Snyk has created this PR to fix one or more vulnerable packages in the `npm` dependencies of this project.

#### Changes included in this PR - Changes to the following files to upgrade the vulnerable dependencies to a fixed version: - backend/package.json - backend/package-lock.json #### Vulnerabilities that will be fixed ##### With an upgrade: Severity | Priority Score (*) | Issue | Breaking Change | Exploit Maturity :-------------------------:|-------------------------|:-------------------------|:-------------------------|:-------------------------  | **776/1000**
**Why?** Recently disclosed, Has a fix available, CVSS 9.8 | Improper Input Validation
[SNYK-JS-SOCKETIOPARSER-3091012](https://snyk.io/vuln/SNYK-JS-SOCKETIOPARSER-3091012) | Yes | No Known Exploit (*) Note that the real score may have changed since the PR was raised.

Commit messages

Package name: socket.io

The new version differs by 57 commits.

• 1af3267 chore(release): 3.0.0
• 02951c4 chore(release): 3.0.0-rc4
• 54bf4a4 feat: emit an Error object upon middleware error
• aa7574f feat: serve msgpack bundle
• 64056d6 docs(examples): update TypeScript example
• cacad70 chore(release): 3.0.0-rc3
• d16c035 refactor: rename ERROR to CONNECT_ERROR
• 5c73733 feat: add support for catch-all listeners
• 129c641 feat: make Socket#join() and Socket#leave() synchronous
• 0d74f29 refactor(typings): export Socket class
• 7603da7 feat: remove prod dependency to socket.io-client
• a81b9f3 docs(examples): add example with TypeScript
• 20ea6bd docs(examples): add example with ES modules
• 0ce5b4c chore(release): 3.0.0-rc2
• 8a5db7f refactor: remove duplicate _sockets map
• 2a05042 refactor: add additional typings
• 91cd255 fix: close clients with no namespace
• 58b66f8 refactor: hide internal methods and properties
• 669592d feat: move binary detection back to the parser
• 2d2a31e chore: publish the wrapper.mjs file
• ebb0575 chore(release): 3.0.0-rc1
• c0d171f test: use the reconnect event of the Manager
• 9c7a48d test: use the complete export name
• 4bd5b23 feat: throw upon reserved event names

See the full diff

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