fix: add WETH on Optimism (#554)

* fix: add WETH on Optimism

Signed-off-by: John Shutt <pemulis@users.noreply.github.com>

* convert optimism weth as upp

Signed-off-by: Reinis Martinsons <reinis@umaproject.org>

* weth store contract on optimism

Signed-off-by: Reinis Martinsons <reinis@umaproject.org>

* update status and upp numbering

Signed-off-by: Reinis Martinsons <reinis@umaproject.org>

Signed-off-by: John Shutt <pemulis@users.noreply.github.com>
Signed-off-by: Reinis Martinsons <reinis@umaproject.org>
Co-authored-by: Reinis Martinsons <reinis@umaproject.org>

UPPs/upp-11.md

@@ -0,0 +1,18 @@
+## Status
+
+Last Call
+
+## Summary
+
+This UPP proposes adding WETH for use as collateral in UMA contracts on Optimism.
+
+## Rationale
+
+WETH is already approved as a collateral currency within UMA's system but has not been approved on Optimism. This UPP will correct that.
+
+## Specifics
+
+To accomplish this upgrade, the following changes need to be made:
+
+-   The Optimism **WETH** address **[0x4200000000000000000000000000000000000006](https://optimistic.etherscan.io/token/0x4200000000000000000000000000000000000006)** needs to be added to the collateral currency whitelist introduced in UMIP-8.
+-   A final fee of **0.35** needs to be added for **WETH** in the Store contract on Optimism.