[#114] Config.extraInfo now optional

[ssawchenko]

Related Issue: #114

Summary of Problem:

When I added the extra info config param I made it non optional, which isn't always desired.

Proposed Solution:

Made property optional

Testing Steps:

To do this I have added a checkbox in the sample app that toggles between setting the property, and having it be set to null.

1. Go to sample app Sentry board https://steamclock-software.sentry.io/issues/?project=5399932 and delete all issues
2. Open sample app and set log level to Release (make sure "add extra config info" checkbox is NOT checked)
3. Press "Send User Report" button
4. Check "add extra config info"
5. Press "Send User Report" button again
6. Go to Sentry board (sometimes you have to wait a few seconds or refresh the board to get the issues to appear)
7. Make sure that there are two issues and that the "newest" issue contains the additional data section, but the oldest issue does not:
   

[phileo]

tested, looks good 👍