feat: add matchers for TemplateLiteral types

[martyy-code]

Description

Add first-class matchers for TypeScript TemplateLiteral types. TemplateLiteral types (e.g. literal string patterns like /users/${string}/posts/${number}) are used in route typing, DSLs, and string parsers. No existing type-testing library tests them.

Why

TemplateLiteral types are increasingly common (Next.js route types, tRPC, Zod schemas). Testing that a utility preserves or transforms template literals correctly is painful today. A dedicated matcher makes this trivial.

Acceptance criteria

• Matcher that extracts the literal parts of a TemplateLiteral type
• Matcher that validates a TemplateLiteral against a pattern
• Tests: infer from template, extract placeholders, match against strings

Risks

• Low. TemplateLiteral is well-specified in TS. The challenge is making error messages readable.

Related

• TypeScript handbook: https://www.typescriptlang.org/docs/handbook/2/template-literal-types.html