When an extension attribute contains a boolean false value, it does not appear in the binary mode HTTP headers. **Steps to Reproduce** ``` const { CloudEvent, HTTP } = require("cloudevents") const ce = new CloudEvent({ type: 'test', source:'testor', exttrue: true, extfalse: false, extstring: 'false' }) const { headers } = HTTP.binary(ce) console.log(headers) // Prints: // { // 'content-type': 'application/json; charset=utf-8', // 'ce-id': '1dcf7357-3896-42d8-afb6-21162d88d550', // 'ce-time': '2022-06-02T16:07:03.729Z', // 'ce-type': 'test', // 'ce-source': 'testor', // 'ce-specversion': '1.0', // 'ce-exttrue': true, // 'ce-extstring': 'false' // } ``` **Expected Behavior** Headers should include expected `ce-extfalse: false`.