Added .packignore support to exclude files from PAKs

[trieck]

Add .packignore support to exclude files from PAK archives

This PR introduces support for a .packignore file, allowing modders to exclude specific files and directories from being packed into .PAK archives. This prevents unwanted files, such as source control folders, temporary logs, or build artifacts, from being included in the final package.

Why This Feature is Needed

Currently, LSLib includes all files within a directory when creating a .PAK, which can lead to temporary build files and other unnecessary files being packed. Until now, modders had to manually remove these files before packaging. This PR provides a clean solution by allowing modders to define exclusions in a .packignore file.

How It Works

The .packignore file is placed in the mod directory and follows a similar syntax to .gitignore, supporting:

• Specific files (debug.log, config.json)
• Folders (bin/, obj/, .git/)
• Wildcards (*.log, *.tmp)

Example .packignore file:

.git/
.vs/
*.bak
*.tmp
.*