* fix: shortcuts with `Option` key

Related to #11 .

* fix: reduce flickering

Related to #25.

Search results flickers because of three things (IMO):

- `handleInput` resets the `results` array, which immediately dropping
  list with `#if` directive in `SearchResult` component
- Changing styles on `focus` and `blur` are not immediate operation, that's why another
  kind of flickering is a transition between focused and non-focused
  state (gray background)
- `getIcon` function is another "bottleneck"; preservation of space for
  upcomming <img> tag is a key for rescue

Most "ugly" part of this code is manipulating with classes. Changing
classes through Svelte's `class:` binding leads to focus lost.

Unfortunately, manipulating classes through script cannot be made with
obfuscated selectors, that's why you can see `:global` in code. Maybe you
know better way to change classes without losing focus.

* fix: span attributes

* fix: remove icon flickering with icons cache

* fix: reset `results` when search pattern is empty

* chore: fix extra rectangular overlay on calculation results

* chore: fix closing window when pressing enter/return

* chore: fix keys not being registered

Co-authored-by: Parth Jadhav <jadhavparth99@gmail.com>

* style: add prettier

style: add prettier ignore file

style: apply formatting

style: install and apply svelte prettier

* Add prettier to recommended extensions

* chore: add check and format scripts to package.json

* chore: update prettier scripts to avoid conflict with svelte-check