VSCode: Highlight parameter placeholders in ScenarioOutline steps

[dotnetprofessional]

Problem

In a ScenarioOutline, step titles contain <parameter> placeholders that correspond to columns in the Examples table. These are not visually distinguished from the rest of the step text, making them harder to spot in code.

scenarioOutline(`Calculate shipping
    Examples:
    | country     | rate          |
    | Australia   | Domestic      |
    | New Zealand | International |
`, () => {
    given("the customer is from <country>", () => { });  // <country> not highlighted
    then("they are charged the <rate> shipping", () => { }); // <rate> not highlighted
});

Current State

The extension provides table header decorations (green styling) but has no TextMate grammar, semantic token provider, or decoration provider for <parameter> patterns in step text.

Proposal

Add a decoration provider that:

1. Detects text matching <\w+> within step function calls (given, when, then, etc.)
2. Applies a distinct visual style (e.g., bold, coloured, or italic) to make parameters stand out
3. Works in both ScenarioOutline and RuleOutline contexts