Add examples for adding static files to language docs

[welteki]

Description

Add examples for adding static files to language docs for Node, Python and PHP.

Motivation and Context

• I have raised an issue to propose this change (required)

Give an example of how to read static files from function templates.

How Has This Been Tested?

Verified the docs render correctly.
Ran the different code examples that were added.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s