chore: Replace eventBus with mitt.js [CW-3275] (#9539)

# Replace the deprecated `eventBus` with mitt.js

## Description

Since eventBus and it's respective methods are deprecated and removed
from all future releases of vue, this was blocking us from migrating.
This PR replaces eventBus with
[mitt](https://github.com/developit/mitt). I have created a wrapper
mitt.js to simulate the same old event names so it's backwards
compatible, without making a lot of changes.


Fixes # (issue)

## Type of change

Please delete options that are not relevant.

- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality not to work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

1. Made sure all the places we're listening to bus events are working as
expected.
2. Respective specsf or the events from mitt.


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

package.json

@@ -31,6 +31,7 @@
   ],
   "dependencies": {
     "@braid/vue-formulate": "^2.5.2",
+    "@chatwoot/ninja-keys": "1.2.3",
     "@chatwoot/prosemirror-schema": "1.0.9",
     "@chatwoot/utils": "^0.0.25",
     "@hcaptcha/vue-hcaptcha": "^0.3.2",
@@ -67,7 +68,7 @@
     "markdown-it": "^13.0.2",
     "markdown-it-link-attributes": "^4.0.1",
     "md5": "^2.3.0",
-    "@chatwoot/ninja-keys": "1.2.3",
+    "mitt": "^3.0.1",
     "opus-recorder": "^8.0.5",
     "postcss": "^8.4.31",
     "postcss-loader": "^4.2.0",