fix: copy over keyboard navigation code and remove plugin dependency (#36)

* feat: copy over base keyboard navigation code and update imports

* chore: remove dependency on @blockly/keyboard-navigation

* feat: use arrow keys in base navigation controller

* chore: used named imports for parts of Blockly

* chore: consolidate navigation controller code

* chore: consolidate line cursor code

* chore: move files out of base_keyboard_nav

* feat: create announcer object

* chore: add comments

* chore: remove unnecessary field shortcut handlers and add a block with a dropdown menu

* chore: format

* chore: add comments

* chore: linting and formatting

* chore: import from blockly/core

Author: rachel-fenichel

package-lock.json

@@ -70,7 +70,6 @@
     "extends": "@blockly/eslint-config"
   },
   "dependencies": {
-    "@blockly/keyboard-navigation": "^0.6.2",
     "p5": "^1.9.4"
   }
 }