Function parse_snippet 

pub fn parse_snippet(snippet: &str) -> SnippetTemplate

Parse a TextMate/VS Code-style snippet string into an expanded template.

Supported constructs (best-effort):

• $1, $2, … tabstops
• ${1}, ${1:default}
• ${1|a,b,c|} (inserts the first option; selects as placeholder)
• $0 / ${0} final caret position
• ${VAR} / ${VAR:default} variables (unresolved; default is used when provided)

Unsupported constructs are ignored or treated as literal text where reasonable.