feat: upgrade maplibre-gl to v3

[JinIgarashi]

This commit is going to change as follows.

• upgraded maplibre-gl to v3 (breaking changes)
• CDN path was changed (breaking changes)

new CDN path

<link href='https://www.unpkg.com/@watergis/maplibre-gl-legend@latest/dist/maplibre-gl-legend.css' rel='stylesheet' />
<script src="https://www.unpkg.com/@watergis/maplibre-gl-legend@latest/dist/maplibre-gl-legend.umd.js"></script>

• introduced pnpm instead of npm/yarn
• introduced monorepo structure by using pnpm workspace
• migrated from webpack to vite
• introduced eslint and prettier

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