docs: change npm and pnpm to be lowercase (#18342)

Author: fyzhu

docs/guide/features.md

@@ -2,7 +2,7 @@
 
 At the very basic level, developing using Vite is not that 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.
 
-## NPM Dependency Resolving and Pre-Bundling
+## npm Dependency Resolving and Pre-Bundling
 
 Native ES imports do not support bare module imports like the following:
 

docs/guide/index.md

@@ -49,15 +49,15 @@ Vite requires [Node.js](https://nodejs.org/en/) version 18+ or 20+. However, som
 
 ::: code-group
 
-```bash [NPM]
+```bash [npm]
 $ npm create vite@latest
 ```
 
 ```bash [Yarn]
 $ yarn create vite
 ```
 
-```bash [PNPM]
+```bash [pnpm]
 $ pnpm create vite
 ```
 
@@ -73,7 +73,7 @@ You can also directly specify the project name and the template you want to use
 
 ::: code-group
 
-```bash [NPM]
+```bash [npm]
 # npm 7+, extra double-dash is needed:
 $ npm create vite@latest my-vue-app -- --template vue
 ```
@@ -82,7 +82,7 @@ $ npm create vite@latest my-vue-app -- --template vue
 $ yarn create vite my-vue-app --template vue
 ```
 
-```bash [PNPM]
+```bash [pnpm]
 $ pnpm create vite my-vue-app --template vue
 ```
 
@@ -118,15 +118,15 @@ In your project, you can install the `vite` CLI using:
 
 ::: code-group
 
-```bash [NPM]
+```bash [npm]
 $ npm install -D vite
 ```
 
 ```bash [Yarn]
 $ yarn add -D vite
 ```
 
-```bash [PNPM]
+```bash [pnpm]
 $ pnpm add -D vite
 ```
 
@@ -146,15 +146,15 @@ Then run the appropriate CLI command in your terminal:
 
 ::: code-group
 
-```bash [NPM]
+```bash [npm]
 $ npx vite
 ```
 
 ```bash [Yarn]
 $ yarn vite
 ```
 
-```bash [PNPM]
+```bash [pnpm]
 $ pnpm vite
 ```