Add guide - Monitoring Lambda Invocation w.r.t cost spikes

[rajlearner17]

Guide purpose
A clear and concise description of what the guide aims to achieve and why it's important.

• Part of /guides/hosting-guardrails/monitoring
• Title: Monitoring Lambda Invocation
• Side Nav Bar: Investigate Lambda Invocation

Content should address as below

• How to monitor lambda invocation in your hosting environment
• Reporting to product team

Target audience
Enterprise hosted environment: Cloud Ops team

Categories
Proposed primary category and categories where this guide would fit best. (e.g., Getting Started, Best Practices, Troubleshooting, Concepts etc).

Outline
A brief outline of the main sections or topics the guide will cover.