Add entire file to context when no text is selected in submodule

[nang-dev]

Original PR by @amovfx
Handles empty selection case
Calls addEntireFileToContext function
Improves user experience
Maintains existing functionality

*Edit by Pan:
Behaviour wanted

• Clicking on a file should add the file tag to the chat. E.g., if I click on file pricing.tsx, then @pricing.tsx should appear in the chat prepended. Like below. And the context of that entire file would be prepended to the chat backend.
• This, way it is non obstructive, and user also knows it is there directly.
• When switching opened files, this current file tag would also change.
  

Description ✏️

Added addEntireFileToContext to addHighlightedCodeToContext when nothing is selected.

[charlwillia6]

@nang-dev - This issue can be closed as we have implemented this. @PearIssueBot

[charlwillia6]

Also, I have a fix for some of the issues with ActiveFileIndicator: trypear/pearai-submodule#159