Add performance-modexp branches (#271)

Signed-off-by: Kamil Chodoła <43241881+kamilchodola@users.noreply.github.com>

Author: kamilchodola

branches.yaml

@@ -8,13 +8,16 @@ besu:
     - main
     - fusaka-devnet-2
     - performance
+    - performance-modexp
 
 erigon:
   branches:
     - main
     - performance
     - berlinterop-devnet-2
     - fusaka-devnet-2
+    - performance-modexp
+    
 ethereumjs:
   branches:
     - master
@@ -27,6 +30,8 @@ geth:
     - performance
     - berlinterop-devnet-2
     - fusaka-devnet-2
+    - performance-modexp
+    
   alt_repos:
     gballet/go-ethereum:
       - kaustinen-with-shapella
@@ -40,6 +45,7 @@ reth:
     - main
     - performance
     - fusaka-devnet-2
+    - performance-modexp
 
 lighthouse:
   branches:
@@ -67,6 +73,7 @@ nethermind:
     - fusaka-devnet-2
     - performance
     - berlinterop-devnet-2
+    - performance-modexp
 
 nimbus-eth2:
   branches: