Update alias documentation

[targhs]

Change Summary

Add usage example for schema field customization alias

Update documentation verbose and add example for using alias

Related issue number

fix #1681

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• changes/<pull request or issue id>-<github username>.md file added describing change
  (see changes/README.md for details)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[targhs]

As its a documentation change, test cases aren't required.

[targhs]

please review

[samuelcolvin]

This is definitely needed, thank you.

Needs some changes:

• needs a whole new section to describe alias
• we need to add docs on the effect of alias with .dict() and .json()

[samuelcolvin]

this will break the bullet points, we should add a whole new section (probably not in schema.py) to document alias.

[samuelcolvin]

please update.

[targhs]

Need your input here.

1. Needs a whole new section to describe
   If not in schema, where? It feels more natural to me if its there along with Unenforced-field-constraints and modifying-schema-in-custom-fields
2. Gotcha

[samuelcolvin]

If not in schema, where?

Sorry for the slow reply, in models.md. Documentation will be rearranged in V2, but that's the best place for now.

please update.

[samuelcolvin]

Notice

See twitter 🐦, I've you'd like this to be included in V1.10, please fix it and request a review TODAY.

Or if you need this in V1.10 but don't have time to complete it (or aren't the author), please comment here and on #4324.

[samuelcolvin]

No reply, closing.

Let me know if you'd like me to re-open this.