chore: replace few import paths ../ with $lib/ (#555)

# Motivation

Not that important but, I spotted few imports in the lib which were
using `../` paths so corrected those with `$lib/`.

src/lib/components/BottomSheet.svelte

@@ -2,7 +2,7 @@
   import { nonNullish } from "@dfinity/utils";
   import { layoutBottomOffset } from "$lib/stores/layout.store";
   import { onDestroy } from "svelte";
-  import { BREAKPOINT_LARGE } from "../constants/constants";
+  import { BREAKPOINT_LARGE } from "$lib/constants/constants";
 
   onDestroy(() => ($layoutBottomOffset = 0));
 

src/lib/components/Island.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import { onDestroy } from "svelte";
-  import { layoutContentScrollY } from "../stores/layout.store";
-  import { BREAKPOINT_LARGE } from "../constants/constants";
+  import { layoutContentScrollY } from "$lib/stores/layout.store";
+  import { BREAKPOINT_LARGE } from "$lib/constants/constants";
 
   export let testId: string | undefined = undefined;
 

src/lib/components/SplitPane.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import { layoutMenuOpen } from "../stores/layout.store";
+  import { layoutMenuOpen } from "$lib/stores/layout.store";
 
   let innerWidth = 0;
 

src/lib/components/StretchPane.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import { layoutMenuOpen } from "../stores/layout.store";
+  import { layoutMenuOpen } from "$lib/stores/layout.store";
   import { BREAKPOINT_LARGE } from "$lib/constants/constants";
 
   let innerWidth = 0;