docs: use npm install in README

Author: afc163

README.md

@@ -70,7 +70,7 @@ export default () => (
 Run the local dumi site:
 
 ```bash
-ut install
+npm install
 npm start
 ```
 
@@ -161,7 +161,7 @@ type ItemType =
 ## Development
 
 ```bash
-ut install
+npm install
 npm start
 npm test
 npm run tsc

README.zh-CN.md

@@ -70,7 +70,7 @@ export default () => (
 运行本地 dumi 站点：
 
 ```bash
-ut install
+npm install
 npm start
 ```
 
@@ -161,7 +161,7 @@ type ItemType =
 ## 本地开发
 
 ```bash
-ut install
+npm install
 npm start
 npm test
 npm run tsc