message: Add method that takes a string and returns a string or null for the evaluate's resolver.
diff: "evaluate": {
  "name": "evaluate",
  "override-signatures": [
  - "evaluate(expression: string, contextNode: Node, resolver: XPathNSResolver | null, type: number, result: XPathResult | null): XPathResult"
  + "evaluate(expression: string, contextNode: Node, resolver: XPathNSResolver | ((prefix: string) => string | null) | null, type: number, result: XPathResult | null): XPathResult"
  ]
  },
  "getElementsByTagNameNS": {
  "evaluate": {
  "name": "evaluate",
  "override-signatures": [
  - "evaluate(expression: string, contextNode: Node, resolver: XPathNSResolver | null, type: number, result: XPathResult | null): XPathResult"
  + "evaluate(expression: string, contextNode: Node, resolver: XPathNSResolver | ((prefix: string) => string | null) | null, type: number, result: XPathResult | null): XPathResult"
  ]
  }
  }
  