Hourly Forecast chart too light and thin

[iamwyh2019]

The lines in hourly forecast chart are too thin and their color too light that it's hard to see the chart under different background:

My solution is to increase the line width and increase opacity, say, change the alpha value of borderColor to 0.5, and add borderWidth=5. It looks like this:

Or we can add a semi-transparent card below the chart. Anyway this is open to discussion.

[iamwyh2019]

Adjusted in #52 (and also fixed the legend unit)