Fixing a typo in confirm.md

[zimventures]

Description

Fixing up a typo in the custom confirmation documentation.

evt is not the correct variable name here - it should be e.

Addresses issue #2989

Testing

Tested locally. Worked A-OK

Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)
• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• I ran the test suite locally (npm run test) and verified that it succeeded

[Telroshan]

Thanks!
Btw, you can directly open PRs to fix the documentation, we just require issues to discuss new features!

[zimventures]

Thanks! Btw, you can directly open PRs to fix the documentation, we just require issues to discuss new features!

Great to know moving forward - thanks @Telroshan!