Persist data like theme, etc to persist between sessions

[Vilayat-Ali]

Do we need this functionality? It can contribute to a better UX

[thtauhid]

This is something we need.

You can take care of this after #76 gets merged.

At the very least we need to store these data-

1. name of the visitor (if they have manually set their name)
2. theme (if they have manually set the theme)

[Vilayat-Ali]

Sure. I will work on jt

[Vilayat-Ali]

Feature implemented in #78