fix(css): updating class names and styles to fix stylebleed issue

[anthony-liddle]

Goal

The options page css styling was being injected into every page being visited (strange behavior)

While fixing we also took this opportunity to make the resets more specific to prevent any other bleeding

Todos:

• [x] Add necessary CSS classes to elements
• [x] Update CSS styling to use updated classes for specificity
• [x] Repeat across all elements

Implementation Decisions

Paired with @wtfluckey on this.

This fixes issue https://github.com/Pocket/extension-save-to-pocket/issues/267

[rodgolpe]

I reported this issue! Thank you for fixing it so quickly! ✌🏻