Minor corrections (#780)

* Transaction outcome

Definition of success and some TVM details.

* Upd transaction outcome

* Update message-delivery-guarantees.mdx

* Update tvm-overview.mdx

* Update message-delivery-guarantees.mdx

* Update academy-overview.md

Button

* op code update

Added known op codes

* Update contracts.md

* Update contracts.md

* Added DEX opcodes

StonFi&DeDust

* Update contracts.md

* Add serokell

docs/develop/companies/outsource.mdx

@@ -11,6 +11,7 @@ Discover 3rd party development teams for your TON project
 * [Coinvent](#coinvent)
 * [EvaCodes](#evacodes)
 * [Pixelplex](#pixelplex)
+* [Serokell](#Serokell)
 * [softstack](#softstack)
 
 ### Astralyx
@@ -130,6 +131,25 @@ PixelPlex stands out in providing secure and scalable blockchain-powered solutio
 - [pixelplex.io](https://pixelplex.io)
 - [[email protected]](mailto:[email protected])
 
+### Serokell
+
+#### Summary
+The most bizarre company with the bravest ideas of Ton and FunC programming.
+
+#### Workstreams
+- Cybersecurity (Smart Contract Audits)
+- Smart Contract & dApp Development
+- Digital Asset Wallets
+
+#### Projects
+- [Symbiosis](https://symbiosis.finance/)
+- [Serokell Case Studies](https://serokell.io/project-ton-blockchain)
+- Delivered TON Wallet Contract security audit
+
+#### Contacts
+- [serokell.io](https://serokell.io/)
+- Telegram [Roman Alterman](https://t.me/alterroman) 
+- [email protected]
 
 ### softstack