Rename CustomTeX example scenes to be more specific.

[Aathish04]

List of Changes

• Rename ExampleFileScene to TexTemplateFromCLI
• Rename ExampleClassScene to InCodeTexTemplate
• Remove comments and rewrite them as docstrings for corresponding Scenes.

Motivation

The "better" way of drawing the end users' attention to how to use the custom TexTemplate related functions was discussed in #199 , and the conversation stopped with @leotrs suggesting that the instructions should probably go in the documentation instead of as comments in the file.

For clarity, ExampleFileScene has been renamed to TexTemplateFromCLI and ExampleClassScene has been renamed to InCodeTexTemplate to better reflect what they demonstrate.

Testing Status

As this is only a name change in an example scene, it shouldn't really impact anything else.
The scenes themselves still work as intended.

Acknowledgement

• I have read the Contributing Guidelines