chore: Add preinstalled example Snap (#27271)

## **Description**

This adds a preinstalled example Snap to the Flask build for testing
purposes.

As requested by @legobeat I removed this change from #27057.  

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## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.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.

app/scripts/snaps/preinstalled-snaps.ts

@@ -4,6 +4,7 @@ import EnsResolverSnap from '@metamask/ens-resolver-snap/dist/preinstalled-snap.
 import AccountWatcherSnap from '@metamask/account-watcher/dist/preinstalled-snap.json';
 ///: BEGIN:ONLY_INCLUDE_IF(build-flask)
 import BitcoinWalletSnap from '@metamask/bitcoin-wallet-snap/dist/preinstalled-snap.json';
+import PreinstalledExampleSnap from '@metamask/preinstalled-example-snap/dist/preinstalled-snap.json';
 ///: END:ONLY_INCLUDE_IF
 
 // The casts here are less than ideal but we expect the SnapController to validate the inputs.
@@ -13,6 +14,7 @@ const PREINSTALLED_SNAPS = Object.freeze<PreinstalledSnap[]>([
   AccountWatcherSnap as PreinstalledSnap,
   ///: BEGIN:ONLY_INCLUDE_IF(build-flask)
   BitcoinWalletSnap as unknown as PreinstalledSnap,
+  PreinstalledExampleSnap as unknown as PreinstalledSnap,
   ///: END:ONLY_INCLUDE_IF
 ]);
 

package.json

@@ -342,6 +342,7 @@
     "@metamask/phishing-controller": "^12.0.1",
     "@metamask/post-message-stream": "^8.0.0",
     "@metamask/ppom-validator": "0.34.0",
+    "@metamask/preinstalled-example-snap": "^0.1.0",
     "@metamask/profile-sync-controller": "^0.8.0",
     "@metamask/providers": "^14.0.2",
     "@metamask/queued-request-controller": "^2.0.0",

yarn.lock

@@ -6044,6 +6044,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@metamask/preinstalled-example-snap@npm:^0.1.0":
+  version: 0.1.0
+  resolution: "@metamask/preinstalled-example-snap@npm:0.1.0"
+  dependencies:
+    "@metamask/snaps-sdk": "npm:^6.5.0"
+  checksum: 10/0540aa6c20b17171f3a3bcf9ea2a7be551d6abbf16de9bd55dce038c5602c62a3921c7e840b82a325b0db00f26b96f54568854bdcd091558bd3b8fa8c6188023
+  languageName: node
+  linkType: hard
+
 "@metamask/profile-sync-controller@npm:^0.8.0":
   version: 0.8.0
   resolution: "@metamask/profile-sync-controller@npm:0.8.0"
@@ -26126,6 +26135,7 @@ __metadata:
     "@metamask/phishing-warning": "npm:^4.0.0"
     "@metamask/post-message-stream": "npm:^8.0.0"
     "@metamask/ppom-validator": "npm:0.34.0"
+    "@metamask/preinstalled-example-snap": "npm:^0.1.0"
     "@metamask/profile-sync-controller": "npm:^0.8.0"
     "@metamask/providers": "npm:^14.0.2"
     "@metamask/queued-request-controller": "npm:^2.0.0"