build: add @vitest/coverage-v8 as a peer dependency extension for vitest

Fixes an issue where running Vitest tests with coverage in a strict pnpm/Bazel environment fails because @vitest/coverage-v8 cannot be found by the vitest execution.

See: vitest-dev/vitest#10025

Author: alan-agius4

package.json

@@ -156,6 +156,11 @@
         "peerDependencies": {
           "protobufjs": "*"
         }
+      },
+      "vitest": {
+        "peerDependencies": {
+          "@vitest/coverage-v8": "*"
+        }
       }
     }
   },