Added support for RTL override character.

[matthew-ivre]

Like a broken record, I'm suggesting that we add support for the RTL override character. It'll let us fix formatting anomalies in the strings.

E.g., closing bracket placed after a URL, and double space before YouTube.

Adding RTLO characters at strategic points in the string forces a fix:

We'd need to make sure that it doesn't actually appear in the string. It shouldn't have a character:

I'm not sure about how to fix this otherwise. Maybe the Arabic translator could rewrite it so there's some Arabic text before the closing bracket.

[matthew-ivre]

Option 1 to remove the character: Go to the fallback font (e.g., Noto Sans), and change the width and height to zero:

[matthew-ivre]

Option 2 to remove the character: I've created a font that contains only the \u202E character - as a narrow space. If you add it as the first option in the fallback list, it's used as the RTLO character:

[matthew-ivre]

Option 3 to remove the character: At the end of LigatureFixer.cs is a check for whether or not to display a character. A ZeroWidthNoJoiner is mentioned, and the RTL override could also be added there:

[matthew-ivre]

See Jira for a solution to force an RTL change (if locale is Arabic) without this PR: https://vreducation.atlassian.net/browse/EN-44052