v3.4.3

• feat: add 404 plugin (#6258) e815aea
• dep: upgrade jest to 26 (#6272) e7772c0
• dep: upgrade open to 8 (#6273) 8b79375
• dep: upgrade postcss to 8 (#6297) e8962d8
• dep: upgrade babel to 7.13, support syntax for typescript 4.2 (#6306) 256b1b3
• fix: add specified umi version to defInfo by default (#6289) 2e3a8c4
• fix(ssr): built-in isBrowser into umi with client (#6082) e37c05e
• fix(ssr): dynamicImport css chunks lost (#6279) 26f9f04
• docs(qiankun): 增加 credentials 配置 (#6302) ea3a7b2
• dep: upgrade react-error-overlay and use-subscription (#6280) e19862d
• Update plugin-initial-state.zh-CN.md (#6285) 49ff850

v3.4.3-beta.1...v3.4.3