fix(js): free native strings #479

Job	Run time
Lint	1m 1s
Build ios Libraries (aarch64-apple-ios)	5m 12s
Build ios Libraries (aarch64-apple-ios-sim)	5m 57s
Build ios Libraries (x86_64-apple-ios)	8m 3s
Build Android Libraries (aarch64-linux-android)	2m 36s
Build Android Libraries (armv7-linux-androideabi)	2m 40s
Build Android Libraries (i686-linux-android)	2m 34s
Build Android Libraries (x86_64-linux-android)	2m 47s
Build Library (linux-aarch64, anoncreds-ubuntu-latest, aarch64-unknown-linux-gnu, libanoncreds.so...	5m 20s
Build Library (linux-x86_64, anoncreds-ubuntu-latest, x86_64-unknown-linux-gnu, libanoncreds.so, ...	4m 43s
Build Library (darwin-x86_64, macos-latest, x86_64-apple-darwin, libanoncreds.dylib)	11m 41s
Build Library (darwin-aarch64, macos-latest, aarch64-apple-darwin, libanoncreds.dylib)	9m 27s
Build Library (darwin-universal, macos-latest, darwin-universal, libanoncreds.dylib)	8m 0s
Build Library (windows-x86_64, anoncreds-windows-latest, windows-x86_64, x86_64-pc-windows-msvc, ...	6m 22s
Test (anoncreds-windows-latest)	6m 5s
Test (anoncreds-ubuntu-latest)	3m 34s
Create android libraries	0s
Create ios xcframework	0s
Create iOS and Android Release Assets	0s
Build and Test JavaScript wrapper	2m 8s
Build Python (anoncreds-ubuntu-latest, linux-aarch64, manylinux2014_aarch64)	20s
Build Python (anoncreds-ubuntu-latest, linux-x86_64, manylinux2014_x86_64)	29s
Build Python (macos-latest, darwin-universal, macosx_10_9_universal2)	32s
Build Python (anoncreds-windows-latest, windows-x86_64, win_amd64)	35s
	1h 30m 6s

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