Adds comprehensive explanation that both files support executors and all
Nx features through the 'nx' property in package.json. Clarifies that
project.json is optional.
Preview:
https://nx-dev-git-issues-28715-nrwl.vercel.app/reference/project-configuration#project-level-configuration-files
## Current Behavior
The documentation for project configuration does not clearly explain
that both package.json and project.json support the same Nx features,
including executors.
## Expected Behavior
The documentation now clearly states that:
- Both package.json and project.json support targets through the "nx"
property in package.json
- The choice between the two is primarily a matter of preference
- Includes an updated example showing how to use `nx.targets` in
package.json
## Related Issue(s)
Fixes#28715
64d0294e4e