fix: add direct ion-icon component import path

[brandyscarney]

Ionic Framework needs the import path otherwise it throws this error:

src/index.ts → dist/...
(!) Plugin typescript: @rollup/plugin-typescript TS2307: Cannot find module 'ionicons/components/ion-icon.js' or its corresponding type declarations.
src/components/IonIcon.ts: (2:37)

2 import { defineCustomElement } from "ionicons/components/ion-icon.js";

Verification steps:

1. Clone this PR branch
2. Install dependencies: npm install
3. Build and pack the project: npm run build && npm pack
4. Copy the .tgz into ~/Downloads: cp ionicons-*.tgz ~/Downloads/ionicons.tgz
5. Navigate to packages/vue in ionic-framework
6. Install the .tgz: npm i ~/Downloads/ionicons.tgz
7. Build Vue: npm run build
8. Observe: Ionic Framework builds successfully

[christian-bromann]

LGTM 👍