FIO-8496: added loading=async for Google Maps JavaScript API

[KatrinKhilko]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-8496

Description

Added loading=async to Google Maps JavaScript API src to prevent console warning.

Dependencies

n/a

How has this PR been tested?

Tested manually

Checklist:

• 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

[johnformio]

@KatrinKhilko I approved, but it has merge conflicts.

[johnformio]

@KatrinKhilko You have merge conflicts