Add a literal for Invariant culture string interpolation

[satikcz]

Add a literal for Invariant culture string interpolation so writing interpolated string with invariant culture is as straightforward as writing interpolated string with current culture.

Something like
config.Add($I"{entry.Key}={entry.Value}")
In the sample I is used as literal that denotes invariant culture interpolated string but that can be literally any available character.

[jnm2]

Today's solution Solution prior to C# 10:

config.Add(FormattableString.Invariant($"{entry.Key}={entry.Value}"));

[333fred]

Actually, it's string.Create(CultureInfo.InvariantCulture, $"{entry.Key}={entry.Value}"). FormattableString is the pre-C# 10 solution.