Add paint events

• Add paint entries "first-paint" and "first-contentful-paint" (see full list below)

• Add experimentation page (npm start)

• Adjust dist to be ES5 compatible (babel)

Example default array after update

0: (2) ["connectEnd", 4.382080078125]
1: (2) ["connectStart", 4.382080078125]
2: (2) ["domComplete", 2165.382080078125]
3: (2) ["domContentLoadedEventEnd", 2111.382080078125]
4: (2) ["domContentLoadedEventStart", 2111.382080078125]
5: (2) ["domInteractive", 2111.382080078125]
6: (2) ["domLoading", 25.382080078125]
7: (2) ["domainLookupEnd", 4.382080078125]
8: (2) ["domainLookupStart", 4.382080078125]
9: (2) ["fetchStart", 4.382080078125]
10: (2) ["loadEventStart", 2165.382080078125]
11: (2) ["requestStart", 4.382080078125]
12: (2) ["responseEnd", 15.382080078125]
13: (2) ["responseStart", 4.382080078125]
14: (2) ["unloadEventEnd", 19.382080078125]
15: (2) ["unloadEventStart", 19.382080078125]
16: (2) ["first-paint", 2049.8999999836087]
17: (2) ["first-contentful-paint", 2049.8999999836087]