Adding a feature : Increase color intensity based on streak

[Lokesh-Bharath]

Description

Adding an option to have the calendar increase the color of the streak circle with increase in streak. This motivates the user to aim and retain a higher streak. The intensity starts low and increases till a 28 days streak. It maxes out at 28 days and thereon shows the same color even with increase in streak.
This option can be enabled or disabled using 'circleColorByStreak' field based on preference.

Fixes # (issue)

#395

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

• If this is a new feature, did you add files to the examples directory to demonstrate the feature?
• If this is a new feature, did you add documentation to the docs directory for the feature?

[Lokesh-Bharath]

Hey @lazyguru, I almost forgot about raising this PR from 2 moths back. The changes are tested, Please feel free to review it and revert back at your convenience

[lazyguru]

Only a minor nit-pick. Thanks again for your contributions!

[lazyguru]

Minor nit-pick: My preference would be to follow the Return Early pattern. Something like this (while longer) is easier to follow mentally:

   while(curStreakCount < 28) {
        let curValue = dataset.getValue(streakStartDate);
        if (curValue == null || curValue == threshold) break;
        if (thresholdType === ThresholdType.GreaterThan && curValue < threshold) break;
        if (thresholdType === ThresholdType.LessThan && curValue > threshold) break;
        curStreakCount++;
        streakStartDate = streakStartDate.subtract(1, "days");
    }