Replace Algolia DocSearch with InstantSearch (#621)

- Rendered only the relevant search results that has the match-level of
either `full` or `partial`.
- Added refinements to display results from other platforms (Active
platform is selected by default).
- Better title and hierarchical display.

![title](https://user-images.githubusercontent.com/13393018/198229684-3018b591-a54c-4b4f-80db-94c11e33ec65.svg)


- Added icons to represent the hierarchy level.

![icons](https://user-images.githubusercontent.com/13393018/198228150-143153bf-aa9a-4c41-baf8-bd9fa3d33bf2.png)
- Relevant results on full/partial match queries.
<img width="595" alt="Screenshot 2022-10-27 at 12 09 26"
src="https://user-images.githubusercontent.com/13393018/198228440-3a7b52a6-9f33-4778-a2ab-15b1454ede99.png">

- TODO: Keyboard shortcut to trigger/focus the search modal. (Will
address this with a new PR)

gulpfile.js

@@ -46,7 +46,7 @@ gulp.task('handleStyle', function() {
 
 // Minify and move JS
 gulp.task('handleJs', function() {
-    return gulp.src (paths.js.main)
+    return gulp.src (paths.js.files)
         .pipe($.terser())
         .pipe(gulp.dest (paths.js.dist))
         .pipe(connect.reload());