fix: Add .e2e as part of the setup script (#9819)

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## **Description**


We missed including the e2e.env file as part of the Copy env vars step
in the setup script. This PR adds the e2e.env file as well as setting
IS_TEST='true' by default in e2e.env.example.

## **Related issues**

Fixes:

## **Manual testing steps**

1. Go to this page...
2.
3.

## **Screenshots/Recordings**

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### **Before**

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### **After**

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## **Pre-merge author checklist**

- [ ] I’ve followed [MetaMask Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

.e2e.env.example

@@ -2,3 +2,4 @@
 export MM_TEST_ACCOUNT_SRP='word1 word... word12'
 export MM_TEST_ACCOUNT_ADDRESS='0x...'
 export MM_TEST_ACCOUNT_PRIVATE_KEY=''
+export IS_TEST="true"

scripts/setup.mjs

@@ -57,7 +57,8 @@ const copyEnvVarsTask = {
       const envFiles = [
         '.js.env',
         '.ios.env',
-        '.android.env'];
+        '.android.env',
+        '.e2e.env'];
       envFiles.forEach((envFileName) => {
         try {
           fs.copyFileSync(`${envFileName}.example`, envFileName, fs.constants.COPYFILE_EXCL);