Core htmx AJAX headers

• should include the HX-Request header9ms ‣

  this.server.respondWith('GET', '/test', function(xhr) {
    xhr.requestHeaders['HX-Request'].should.be.equal('true')
    xhr.respond(200, {}, '')
  })
  var div = make('<div hx-get="/test"></div>')
  div.click()
  this.server.respond()