chore: use git submodules for conformance tests (#427)

I don't think downloading to `/tmp` for each `npm test` is such a great
idea. This does mean that contributors to this repo will need to run the
following command once on their clone after this commit lands.

```
git submodule init
git submodule update
```

Signed-off-by: Lance Ball <lball@redhat.com>

.github/workflows/nodejs-ci-action.yml

@@ -32,6 +32,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: true
     - name: Generate coverage report
       uses: actions/setup-node@v1
       with:

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "conformance"]
+	path = conformance
+	url = git@github.com:cloudevents/conformance.git

conformance

@@ -0,0 +1 @@
+Subproject commit eddc279339609ed92d128bcd2b0d5c558a7ce396

package.json

@@ -12,7 +12,7 @@
     "lint:fix": "eslint 'src/**/*.{js,ts}' 'test/**/*.{js,ts}' --fix",
     "pretest": "npm run lint && npm run conformance",
     "test": "mocha --require ts-node/register ./test/integration/**/*.ts",
-    "conformance": "npx downtotemp https://raw.githubusercontent.com/cloudevents/conformance/master/features/http-protocol-binding.feature && cucumber-js /tmp/http-protocol-binding.feature -p default",
+    "conformance": "cucumber-js ./conformance/features/http-protocol-binding.feature -p default",
     "coverage": "nyc --reporter=lcov --reporter=text npm run test",
     "coverage-publish": "wget -qO - https://coverage.codacy.com/get.sh | bash -s report -l JavaScript -r coverage/lcov.info",
     "generate-docs": "typedoc --excludeNotDocumented --out docs src",
@@ -125,7 +125,6 @@
     "cucumber": "^6.0.5",
     "cucumber-pretty": "^6.0.0",
     "cucumber-tsflow": "^3.2.0",
-    "downtotemp": "^0.1.2",
     "eslint": "^7.32.0",
     "eslint-config-prettier": "^8.3.0",
     "eslint-config-standard": "^16.0.3",