feat: Add spawn vim docs

[deepanchal]

Description

This PR adds how-to-spawn-vim documentation under Recipes > Applications > Spawn External Editor (Vim)

I am now using hello-world-template as base for my example to keep things simple (https://github.com/ratatui-org/ratatui-website/pull/651/commits/31fc71c8d3fa99dd182871c47f6ea14c35617f45) and I have added logic to spawn vim in a separate commit (https://github.com/ratatui-org/ratatui-website/pull/651/commits/8380d5b4185879745350cc1d613d70acbc91e81f).

I am not familiar with astro but I tried to use other examples as reference to write this documentation. Please let me know if I missed anything. Thanks!!

Related Issue

Ref #406

Images