Add terminal setup color guidance for good experience with kalk

[xoofx]

kalk is relying on standard ANSI escape code colors to select the colors for syntax highlighting.

We don't want necessarily to use other colors (e.g user defined with full RGB escape sequences) but would like to only rely on these standard escape code.

The supported colors are the following, and kalk is using only a subset of them:

• Black
• Red -> kalk errors
• Green
• Yellow -> kalk units
• Blue
• Magenta
• Cyan -> kalk built-in functions/values
• White -> kalk anything else
• Bright Black (Gray)
• Bright Red
• Bright Green -> kalk comments
• Bright Yellow -> kalk keywords
• Bright Blue
• Bright Magenta
• Bright Cyan -> kalk VerbatimString
• Bright White -> kalk name followed by a :

The code involved is here:

kalk/src/Kalk.Core/KalkEngine.Highlight.cs

Lines 651 to 698 in 18a486e

	private ConsoleStyle? GetStyle(int index, Token token, string text, bool isPreviousNotDot, List<Token> tokens)
	{
	switch (token.Type)
	{
	case TokenType.Integer:
	case TokenType.HexaInteger:
	case TokenType.BinaryInteger:
	case TokenType.Float:
	return ConsoleStyle.Bold;
	case TokenType.String:
	case TokenType.VerbatimString:
	return ConsoleStyle.BrightCyan;
	case TokenType.Comment:
	case TokenType.CommentMulti:
	return ConsoleStyle.BrightGreen;
	case TokenType.Identifier:
	var key = token.GetText(text);
	if (isPreviousNotDot)
	{
	if ((index + 1 < tokens.Count && tokens[index + 1].Type == TokenType.Colon))
	{
	return ConsoleStyle.BrightWhite;
	}
	if (ScriptKeywords.Contains(key))
	{
	// Handle the case where for ... in, the in should be marked as a keyword
	if (key != "in" || !(index > 1 && tokens[index - 2].GetText(text) == "for"))
	{
	return ConsoleStyle.BrightYellow;
	}
	}
	if (Builtins.ContainsKey(key) || ValueKeywords.Contains(key))
	{
	return ConsoleStyle.Cyan;
	}
	else if (Units.ContainsKey(key))
	{
	return ConsoleStyle.Yellow;
	}
	}
	return ConsoleStyle.White;
	default:
	return null;
	}
	}

We should add some guidance to the documentation on how to configure these colors (e.g in new Windows terminal)

Accessorily, do we need to improve the syntax highlighting?