feat: add bss-core unit tests to GH actions

This was overlooked when
https://github.com/ethereum-optimism/optimism/pull/2107 was merged.

.github/workflows/bss-core.yml

+name: bss-core unit tests
+
+on:
+  push:
+    paths:
+      - 'go/bss-core/**'
+    branches:
+      - 'master'
+      - 'develop'
+      - '*rc'
+      - 'regenesis/*'
+  pull_request:
+    paths:
+      - 'go/bss-core/*'
+  workflow_dispatch:
+
+defaults:
+  run:
+    working-directory: './go/bss-core'
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.16.x
+
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Test
+        run: go test -v ./...

.github/workflows/golangci-lint.yml

@@ -29,3 +29,8 @@ jobs:
         with:
           version: v1.29
           working-directory: go/batch-submitter
+      - name: golangci-lint bss-core
+        uses: golangci/golangci-lint-action@v2
+        with:
+          version: v1.29
+          working-directory: go/bss-core