.github: add @gballet as abi codeowner (#18306)

gballet · fjl · commit aebf9e2fe7be · 2018-12-14T15:05:22.000+01:00
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
@@ -2,6 +2,7 @@
 # Each line is a file pattern followed by one or more owners.
 
 accounts/usbwallet              @karalabe
+accounts/abi                    @gballet
 consensus                       @karalabe
 core/                           @karalabe @holiman
 eth/                            @karalabe
