Add `pinia` snippets

[ExEr7um]

Snippets for Pinia store.

There are 2 pull requests on original repository:

• Adds Pinia snippets sdras/vue-vscode-snippets#108 by @CRBroughton
• add snippet for pinia store sdras/vue-vscode-snippets#107 by @danielkellyio

I should these people to co-authors of commit and to contributors.