1. Bump all minor and patch versions of all packages.
2. Upgrade `autoprefixer`: Use `.browserslistrc` and delete `.postcssrc`
 Add it to `postcss.config.js`
 Install and add `postcss-preset-env` to `postcss.config.js`
3. Upgrade `immutable`: Explicitly convert all `Array`s to `List`s
4. Upgrae `marked`: Install `marked-gfm-heading-id` to support `gfm` opt
5. Upgrade `react-router`:
 a. Remove `exact`
 b. Use `Routes` instead of `Switch`.
 c. Import `StaticRouter` from `react-router-dom/server`.
 d. Use `element` instead of `component`
 e. Use absolute paths instead of relative in Links.
 f. Convert Two Components to Functional React ones in order to use
 `useLocation` hook.
 g. Use `isActive` in `className` instead of `activeClassName`.
 h. Use `Navigate` instead of `Redirect`.
 i. Reset state once redirected.
6. Upgrade `react-transition-group`:
 a. Use `TransitionGroup` and `CSSTransition` instead of
 `ReactCSSTransitionGroup`.
 b. Convert one component to a Functional React one to use `forwardRef`
 c. Add `nodeRef` as part of the state to track DOM nodes for animation
7. Install `typescript` because it's a needed peer depenency of
 `prettier-eslint-cli`
Signed-off-by: Khaled Emara <mail@KhaledEmara.dev>