Core htmx AJAX headers

• request to restore history should include the HX-Current-URL header4ms ‣

  this.server.respondWith('GET', '/test', function(xhr) {
    chai.assert(typeof xhr.requestHeaders['HX-Current-URL'] !== 'undefined', 'HX-Current-URL should not be undefined')
    xhr.respond(200, {}, '')
  })
  htmx._('loadHistoryFromServer')('/test')
  this.server.respond()