chore(docs): api-plugin and features apply outline deep (vitejs#14282)

Author: btea

docs/guide/api-plugin.md

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 # Plugin API
 
 Vite plugins extends Rollup's well-designed plugin interface with a few extra Vite-specific options. As a result, you can write a Vite plugin once and have it work for both dev and build.

docs/guide/features.md

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 # Features
 
 At the very basic level, developing using Vite is not that much different from using a static file server. However, Vite provides many enhancements over native ESM imports to support various features that are typically seen in bundler-based setups.