chore: add frontend mention to readme

[Kaladin13]

Closes #99

[Copilot]

Pull Request Overview

Adds a reference to the frontend dApp and an “Examples and usage” section with live testnet links for contracts and transactions.

• Introduce T-Dex frontend dApp link and repo
• Add “Examples and usage” section listing deployed contracts and sample transactions

Comments suppressed due to low confidence (4)

README.md:11

• [nitpick] Consider capitalizing 'WIP' or spelling out 'work-in-progress' for clarity.

Check out T-Dex wip dApp frontend to perform swaps with web UI:

README.md:16

• Change 'this example' to 'these examples' to match the plural context of multiple links.

You can use this example to see how to integrate with T-Dex contracts from the frontend or execute swap transactions.

README.md:40

• If the README includes a table of contents, update it to include the new 'Examples and usage' section for easier navigation.

## Examples and usage

README.md:53

• [nitpick] Since this link no longer exists, consider removing this bullet or noting that the resource is archived/removed for clarity.

- [Proxy liquidity deposit](https://testnet.tonviewer.com/0QBa3_cmTS4lg_pGBt_k5t1NEfHFnsDm8Y2UkD_t3MCQHAG7) (Non-existent because was destroyed after tx)