Add Audits folder and audit reports (#2272)

Adding an Audits folder, containing the external audits and internal
reviews which can also be found in
[espresso-audits](https://github.com/EspressoSystems/espresso-audits).

Audits/README.md

@@ -0,0 +1,17 @@
+# Espresso-audits
+
+External audits
+
+| Team                                           | Scope & Delivery date                    | Report                                                            |
+| ---------------------------------------------- | ---------------------------------------- | ----------------------------------------------------------------- |
+| [Common Prefix](https://www.commonprefix.com/) | Plonk verifier - September 2, 2024       | [Reports](./external-reviews/EspressoPlonk-2024.pdf)              |
+| [Common Prefix](https://www.commonprefix.com/) | Light Client Contract - November 8, 2024 | [Reports](./external-reviews/EspressoHotshotLightClient-2024.pdf) |
+
+Internal audits
+
+| Scope & Delivery date                                                | Report                                                             |
+| -------------------------------------------------------------------- | ------------------------------------------------------------------ |
+| Fee Contract - August 2, 2024                                        | [Reports](./internal-reviews/EspressoFeeContract-2024internal.pdf) |
+| Functions new_legacy and validate_and_apply_header - October 4, 2024 | [Reports](./internal-reviews/EspressoSequencer-2024internal.pdf)   |
+
+A compilation of all audit report can also be viewed [here](https://github.com/EspressoSystems/Espresso-audits).