⚡️ Added a page on security best practices to the documentation

There are several anti-patterns and potential attack vectors that Tact smart contract developers should be aware of. These can affect the security, efficiency, and correctness of the contracts.

With the help of community contributors, we've discussed the do's and don'ts specific to writing and maintaining secure Tact smart contracts, and written a cohesive page for you!

🧑‍🍳🎉 Community contributors: PixelPlex and Aliaksandr Bahdanau
🐙 Implementation: #1070
✈️ Delivered: docs.tact-lang.org/book/security-best-practices

🍲 where did the bad actor go? they ran somewhere
♨️ @tact_kitchen