added new feature - set custom background color

[shalithasuranga]

Now background color of output image can be selected at the beginning. fixes 2 items of #27 checklist

[rehrumesh]

This is something you proposed new? Can you link the issue please? Otherwise before work on something new, better to discuss with the team.

@chamathpali please check this.

[chamathpali]

@shalithasuranga this is a good feature to have. Keep white as default since this will be directly embedded in Readme's of repos. Also is there any impact on the file size with color and without color?

[shalithasuranga]

@rehrumesh This PR connects #27 . Okay Next time I will discuss before implement something. Thanks

[shalithasuranga]

@chamathpali

Here is the comparison of files.

Output of current version 62KB

PR version background "#ffff00" and opacity 1 75KB

PR version background "#ffff00" and opacity 0.5 73KB

PR version background "#ffff00" and opacity 0 71KB

Large files

Current version : 3.3 MB PR version background "#ffff00" and opacity 1 : 4.1 MB

it seems there is bit increase in size when colors added and opacity in mid value We are not able to generate alpha levels in jpg. That's why I changed to .png Your ideas please

Thanks

[rehrumesh]

@chamathpali Please review

[chamathpali]

Thanks @shalithasuranga 👍 Good work