feat: add monad to network enablement controller (#6978)

## Explanation

Adds monad to network enablement controller constants 
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## References

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## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [ ] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds Monad (chainId 0x8f / 143) to POPULAR_NETWORKS and updates the
changelog.
> 
> - **Network Enablement Controller**:
> - Add `0x8f` (Monad, 143) to `POPULAR_NETWORKS` in
`packages/network-enablement-controller/src/constants.ts`.
> - **Changelog**:
> - Document the addition under `Unreleased` in
`packages/network-enablement-controller/CHANGELOG.md`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
d098ad8. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: khanti42

packages/network-enablement-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add Monad network into constant POPULAR_NETWORKS ([#6978](https://github.com/MetaMask/core/pull/6978))
+
 ## [3.0.0]
 
 ### Changed

packages/network-enablement-controller/src/constants.ts

@@ -11,4 +11,5 @@ export const POPULAR_NETWORKS = [
   '0x144', // zkSync Era (324)
   '0x2a15c308d', // Palm (11297108109)
   '0x3e7', // HyperEVM (999)
+  '0x8f', // Monad (143)
 ];