Add C template with GCC and Make support

[shaiksahilrizwan]

This PR adds a new community template for the C programming language.

Features

• Compiler: GCC configured and ready to use.
• Build System: Includes make support.
• Debugging: gdb installed.
• Editor Integration: Pre-installs the ms-vscode.cpptools and danielpinto8zz6.c-cpp-compile-run extension for syntax highlighting, debugging and running.

Optional

• Auto-build: Configured to compile and run the application automatically using buildAndRun.
  -- Build Tools: make and gdb installed for future extensibility.

Files Added

• dev.nix: Defines the Nix environment with gcc, gnumake, gdb.
• idx-template.nix: Bootstrap script to set up the workspace.
• idx-template.json: Template metadata.
• Starter code (main.c).

This allows users to quickly spin up a C development environment in Project IDX.

[shaiksahilrizwan]

Hi everyone, I've enabled the "Allow edits from maintainers" option. So please feel free to make any necessary changes directly. I'm happy to learn from your feedback!