Do not warn about @emotion/react being loaded twice in Vitest (#2905)

* Check vitest global for @emotion/react loaded twice warning

* code review tweaks

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

.changeset/loud-dancers-return.md

@@ -0,0 +1,5 @@
+---
+'@emotion/react': patch
+---
+
+Do not warn about `@emotion/react` being loaded twice in Vitest as that might easily happen with mocked modules.

flow-typed/npm/vitest_vx.x.x.js

@@ -0,0 +1 @@
+declare var vi: {}

packages/react/src/index.js

@@ -16,10 +16,10 @@ export { default as css } from './css'
 
 if (process.env.NODE_ENV !== 'production') {
   const isBrowser = typeof document !== 'undefined'
-  // #1727 for some reason Jest evaluates modules twice if some consuming module gets mocked with jest.mock
-  const isJest = typeof jest !== 'undefined'
+  // #1727, #2905 for some reason Jest and Vitest evaluate modules twice if some consuming module gets mocked
+  const isTestEnv = typeof jest !== 'undefined' || typeof vi !== 'undefined'
 
-  if (isBrowser && !isJest) {
+  if (isBrowser && !isTestEnv) {
     // globalThis has wide browser support - https://caniuse.com/?search=globalThis, Node.js 12 and later
     const globalContext =
       // $FlowIgnore