[modules][expo-document-picker] Support picking multiple documents (#20365)

# Why
I've seen this feature being asked for a couple of times on discord or Twitter.

# How
Added support for pickin

[modules][expo-document-picker] Support picking multiple documents (#20365)

# Why
I've seen this feature being asked for a couple of times on discord or Twitter.

# How
Added support for picking multiple documents on both platforms

# Test Plan
Tested the new behaviour in the bare expo app.

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