node: add sequelize + express + opentelemetry sample app

nodejs/sqlcommenter-nodejs/samples/express-opentelemetry/README.md

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+# Express + OpenTelemetry example app
+
+This example Express app connects to a Cloud SQL database (Postgres or MySQL)
+using Sequelize or Knex as the ORM. It is instrumented with OpenTelemetry to
+collect trace data and send it to Cloud Trace. SQLCommenter attaches the
+OpenTelemetry trace and span ID to the queries for correlation.
+
+## Running
+
+This example reads some environment variables to connect to a Cloud SQL database.
+
+- `DBHOST` - The hostname, ip, or path to unix socket directory for Cloud SQL
+database. For example, if you are using Cloud SQL proxy with a unix socket,
+you might pass `/cloudsql/my-project:us-central1:my-db`
+- `DBUSERNAME` - Database username
+- `DBPASSWORD` - Database password
+- `DBDIALECT` - Optional. Should be `postgres` (default) or `mysql`
+
+```bash
+# in this directory
+$ export DBHOST="<hostname or unix socket path>"
+$ export DBUSERNAME="<database user>"
+$ export DBPASSWORD="<database password>"
+$ export DBDIALECT="<postgres | mysql>"
+$ npm install
+
+# on first run, create some data
+$ npm run createTodos
+
+# run the sequelize server
+$ npm run sequelizeServer
+
+# in a separate terminal
+$ curl http://localhost:8000
+{"todos":[{"id":11,"title":"Do dishes","description":null,"done":false,"createdAt":"2020-11-06T01:59:50.111Z","updatedAt":"2020-11-06T01:59:50.111Z"},{"id":12,"title":"Buy groceries","description":null,"done":false,"createdAt":"2020-11-06T01:59:50.111Z","updatedAt":"2020-11-06T01:59:50.111Z"},{"id":13,"title":"Do laundry","description":"Finish before Thursday!","done":false,"createdAt":"2020-11-06T01:59:50.111Z","updatedAt":"2020-11-06T01:59:50.111Z"},{"id":14,"title":"Clean room","description":null,"done":false,"createdAt":"2020-11-06T01:59:50.111Z","updatedAt":"2020-11-06T01:59:50.111Z"},{"id":15,"title":"Wash car","description":null,"done":false,"createdAt":"2020-11-06T01:59:50.112Z","updatedAt":"2020-11-06T01:59:50.112Z"}]}
+
+# Original terminal will output
+[server]: Server is running at https://localhost:8000
+Google Cloud Trace export
+Google Cloud Trace batch writing traces
+Google Cloud Trace authenticating
+Google Cloud Trace got authentication. Initializaing rpc client
+batchWriteSpans successfully
+Executing (default): SELECT "id", "title", "description", "done", "createdAt", "updatedAt" FROM "Todos" AS "Todo" LIMIT 20; /*client_timezone='%2B00%3A00',db_driver='sequelize%3A6.3.3',route='%2F',traceparent='00-3e2914ebce6af09508dd1ff1128493a8-81d09ab4d8cde7cf-01'*/
+Executing (default): SELECT "done", COUNT("id") AS "count" FROM "Todos" AS "Todo" GROUP BY "done"; /*client_timezone='%2B00%3A00',db_driver='sequelize%3A6.3.3',route='%2F',traceparent='00-3e2914ebce6af09508dd1ff1128493a8-81d09ab4d8cde7cf-01'*/
+Google Cloud Trace export
+Google Cloud Trace batch writing traces
+batchWriteSpans successfully
+```