Update README.md for supporting angular 19

[krishnpalchouhan]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-XXXX

Description

What changed?

Just updated angular support version for angular 19

Why have you chosen this solution?

as angular 19 is already implimented it should also be there in README.md file.

Breaking Changes / Backwards Compatibility

No breaking changes as only README file change

Dependencies

Use this section to list any dependent changes/PRs in other Form.io modules

How has this PR been tested?

No testing is required

Checklist:

• I have completed the above PR template
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above