npm: add basic example from sample-nodejs-app

Migrate the basic npm sample from cachito-testing/sample-nodejs-app to doc-examples and adapt it to use Hermeto for npm dependencies.

Signed-off-by: Vladimir Aleksandrov <valeksan@redhat.com>

Author: derasdf

.dockerignore

@@ -0,0 +1,3 @@
+.git
+node_modules
+

Containerfile

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+FROM node:18
+
+WORKDIR /src
+
+COPY . .
+
+RUN npm install --verbose
+
+EXPOSE 9000
+
+CMD ["node", "index.js"]
+

index.js

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+const express = require("express");
+
+const port = 9000;
+const app = express();
+
+app.get("/", (req, res) => res.send("Hello Dude!"));
+
+app.listen(port, () => console.log(`App started on port ${port}...`));