Embed Snapshot screenshot in Snapshot file

[Remi05]

It would be more convenient for many scenarios to have Snapshots be contained in a single file. To do so, we could convert the screenshot to Base64 and serialize it as part of the Snapshot JSON. We should try to make sure the image's Base64 string is the last value in the JSON so that the rest of the values can still be read by humans without searching for them. We could eventually provide a setting to allow for saving the screenshot separately (or both).

Useful links:

• https://docs.microsoft.com/en-us/dotnet/api/system.convert.tobase64string?view=net-5.0
• https://www.newtonsoft.com/json/help/html/JsonPropertyOrder.htm

[Remi05]

Added with commit 368c5875161fa2dacd30e86eb4e03866d9fd993e.