Support Angular 20 and CDK v20 compatibility

[yamashin4645]

Hi 👋

Thanks for maintaining this great library!

I'm currently migrating my project to Angular 20, but I noticed that ng2-date-picker has a strict peer dependency on @angular/* and @angular/cdk up to v19.

Would it be possible to update the peerDependencies to support Angular 20 and CDK v20?

"peerDependencies": {
  "@angular/common": "^16.0.0 || ^17.0.0 || ^18.0.0 || ^19.0.0 || ^20.0.0",
  "@angular/core": "^16.0.0 || ^17.0.0 || ^18.0.0 || ^19.0.0 || ^20.0.0",
  "@angular/cdk": "^19.0.0 || ^20.0.0"
}

Also, it might be helpful to check for any breaking changes in CDK Overlay or PositionStrategy that could affect popup behavior.

Thanks again!

[nstdspace]

I submittted a pr to upgrade to angular 20