Add README for .devcontainer folder (run-llama#46)

* add README for .devcontainer folder

* spelling

* spelling

* typo

Author: sourabhdesai

.devcontainer/README.md

@@ -0,0 +1,25 @@
+# SEC Insights Dev Container
+
+This dev container configuration sets up a development environment that is specifically configured for this project.
+
+This is useful in getting the project setup faster by having many of the system dependencies already pre-installed.
+
+## How do I use this?
+
+You can either click this button to open the dev container on a Github Codespace:
+
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/run-llama/sec-insights)
+
+Or you can spin up the dev container up locally using [VS Code's dev container feature](https://code.visualstudio.com/docs/devcontainers/create-dev-container#_create-a-devcontainerjson-file).
+
+## What are the benefits of using this?
+* System level dependencies are pre-installed
+  * Project-specific python version
+  * Other dependencies like `wkhtmltopdf` & `s3fs` are pre-installed
+  * Uses the same base Docker image as what's used for the production service
+    * So higher fidelity between your dev environment and prod environment.
+
+## Are there any downsides to using this?
+One downside is that when you're using the dev container via Github Codespaces, that service isn't entirely free. There's a free tier limit after which Github Codespace usage is paid.
+Also, if you're running the dev container locally via the VS Code dev container feature, you may find that Docker can take up quite a bit of storage space on your machine. Make sure you have the necessary storage space.
+