chore: add get current route helper

[MounirDhahri]

This PR resolves []

Description

This PR adds a helper method to get the active URL - ready to share.
I needed to do this manually because 1. useLinkBuilder from react-navigation doesn't work in our infra and 2. doesn't support the nested routes we use (AFAIK).

I needed this to work on a future Friday project that unfortunately didn't work out well. I created this PR to save a future me or other engineer in Artsy the time and hassle that was required to build this.

@brainbicycle I know you are working on some navigation stuff, this might be useful to you - who knows

PR Checklist

• I have tested my changes on iOS and Android.
• I hid my changes behind a feature flag, or they don't need one.
• I have included screenshots or videos, or I have not changed the UI.
• I have added tests, or my changes don't require any.
• I added an app state migration, or my changes do not require one.
• I have documented any follow-up work that this PR will require, or it does not require any.
• I have added a changelog entry below, or my changes do not require one.

To the reviewers 👀

• I would like at least one of the reviewers to run this PR on the simulator or device.

Changelog updates

Changelog updates

Cross-platform user-facing changes

• add get current route helper - mounir

iOS user-facing changes

Android user-facing changes

Dev changes

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