Migrate the CSS to in-component

[jeremy-jtlo]

Per the discussion offline, it's been decided that we'll sunset the explicit .css files and move forward with React Component styling.

Files to migrate/deprecate:

• PokemonDisplayStyle.css
• PokemonSearch.css
• App.css
• index.css

Because React allows us to define styles as objects in our components, it gives us the power to leverage explicit TS logic to define how a component renders, rather than learning too hard on media queries or assigning different classes based on state.

[gdirk07]

As per a later issue, we are going with Material UI, will close this issue when the changes are made

[gdirk07]

Closed with the merge of #39