Add GitHub bootstrap e2e test

.github/workflows/bootstrap.yaml

+name: bootstrap
+
+on:
+  push:
+    branches:
+      - master
+      - refac
+
+jobs:
+  github:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Restore Go cache
+        uses: actions/cache@v1
+        with:
+          path: ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
+      - name: Setup Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.14.x
+      - name: Setup Kubernetes
+        uses: engineerd/setup-kind@v0.4.0
+        with:
+          image: kindest/node:v1.16.9
+      - name: Set outputs
+        id: vars
+        run: echo "::set-output name=sha_short::$(git rev-parse --short HEAD)"
+      - name: Build
+        run: sudo go build -o ./bin/gotk ./cmd/gotk
+      - name: gotk bootstrap github
+        run: |
+          ./bin/gotk bootstrap github \
+          --owner=fluxcd-testing \
+          --repository=gotk-test-${{ steps.vars.outputs.sha_short }} \
+          --path=test-cluster
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITPROVIDER_BOT_TOKEN }}
+      - name: Debug failure
+        if: failure()
+        run: |
+          kubectl -n gitops-system get all
+          kubectl -n gitops-system logs deploy/source-controller
+          kubectl -n gitops-system logs deploy/kustomize-controller