Add 4337 Module v0.2.0 Audit Report (#185)

Closes #168 

This PR adds the audit report for the v0.2.0 version of the canonical
4337 module along with a "known issues" section to the v0.1.0 version of
the module.

4337/docs/v0.1.0/audit.md

@@ -1,3 +1,5 @@
+**:warning: This version contains known issues and should not be used. :warning:**
+
 # Audit Results
 
 ## Auditor
@@ -21,3 +23,7 @@ There are two acknowledged findings from the audit report:
 ## Files
 
 - [Final audit report](audit-report-v1.1.pdf)
+
+## Known Issues
+
+The contract does not include all the User Operation parameters in its signature mechanism. Notably, the two missing parameters are `initCode` and `paymasterAndData`. This allows a malicious actor to execute a Safe operation with different `initCode` (causing potentially additional gas fees to the user) or `paymasterAndData` (causing the user to pay for gas fees in Ether despite not expecting it) than what the user originally intended. See section _M1_ from the [v0.2.0 audit report](../v0.2.0/audit-report-v2.0.pdf).

4337/docs/v0.2.0/audit.md

@@ -0,0 +1,21 @@
+# Audit Results
+
+## Auditor
+
+Ackee Blockchain (<https://ackeeblockchain.com/>).
+
+## Notes
+
+The final audit was performed on commit [25779b5a5077e109a585993a02c4dad2209ab084](https://github.com/safe-global/safe-modules/tree/25779b5a5077e109a585993a02c4dad2209ab084).
+
+There is one acknowledged finding from the audit report:
+
+- _W2: Usage of `solc` optimizer_
+  > After careful consideration, we decided to enable the optimizer for the following reasons:
+  >
+  > - The most critical functionality, such as signature checks and replay protection, is handled by the Safe and Entrypoint contracts.
+  > - The entrypoint contract uses the optimizer.
+
+## Files
+
+- [Final audit report](audit-report-v2.0.pdf)