switch Readme version badge source to shields.io

[Simek]

Summary

Lately there are some loading issues for the fury.io badges service which results in missing image and alt text visible in the Readme.

This PR fixes that issue by switching to shields.io version badge - badge service that has been used for few other badges already.

Changelog

[Internal] [Changed] - change Readme npm version badge to shields.io

Test Plan

All badges will appear in the Readme file. 🙂

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: 2669118

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	7,525,501	+0
android	hermes	armeabi-v7a	7,110,737	+0
android	hermes	x86	7,965,962	+0
android	hermes	x86_64	7,877,257	+0
android	jsc	arm64-v8a	8,989,758	+0
android	jsc	armeabi-v7a	8,558,104	+0
android	jsc	x86	8,991,720	+0
android	jsc	x86_64	9,543,270	+0

Base commit: 2669118

[facebook-github-bot]

@hramos has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[react-native-bot]

This pull request was successfully merged by @Simek in 8cc4467.

^{When will my fix make it into a release? | Upcoming Releases}