✨ Extension method to convert a string to `ReadOnlySpan<Rune>`

[candoumbe]

Is your feature request related to a problem? Please describe.
string type has implicit conversion to ReadOnlySpan<char> but no implicit conversion to ReadOnlySpan<Rune>.

This could be handy when dealing with text that may content emojis and might be more robust than the naïve char approach

Describe the solution you'd like
A way to convert string or ReadOnlySpan<char> to ReadOnlySpan<Rune>

Describe alternatives you've considered
N/A

Additional context
Some articles that might help getting started :

• Character encoding in .NET
• How to correctly count the number of characters of a string