docs(env): add env.example to show the app available options

.env.example

@@ -0,0 +1,23 @@
+# The ID of your GitHub App
+APP_ID=
+
+# Holds a secret to identify github against the app (app checks that github
+# is legit)
+WEBHOOK_SECRET=secret
+
+# Use `trace` to get verbose logging or `info` to show less
+LOG_LEVEL=debug
+
+# If set to true, requests answers will be saved to a file
+# based on the use of createFixture(name).
+# the file is saved with a suffix of `autosave`, which is ignored by git.
+# to commit a request response dump, change the name and remove the autosave
+# suffix
+fixtures=true
+
+# Go to https://smee.io/new set this to the URL that you are redirected to.
+WEBHOOK_PROXY_URL=
+
+# Holds the private key to identify the github app (github checks that app is
+# legit)
+PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----\n..."

.gitignore

@@ -1,5 +1,6 @@
 node_modules/
 .env*
+!.env.example
 package-lock.json
 .idea
 test-results/