added download app section

[rowhitswami]

Fixes issue #24

Changes: decreased the code redundancy of sponsors sections. Now the same block of code will serve for both desktop and mobile users. Also added a 'Download App' section which can be used whenever the app is ready.

Screenshots for the change:

Sponsors Section

Download App Section

And here mobile view of both changes

[ashwini0529]

@rowhitswami You've App Store image in your commit. Please remove that.

[rowhitswami]

@ashwini0529 Done :)

[ashwini0529]

Here you go @rowhitswami ! :)

[rowhitswami]

@ashwini0529 Thank you. Please let me know if you face any issue regarding design and layout in future. I'd love to do it.

[technophilic]

@ashwini0529 this commit breaks the sponsors section of mobile layout. In fact it is even a little absurd for desktop layout in my opinion. What should be done?

[rowhitswami]

@ashwini0529 Please suggest any improvement