Feature: Follow symlinks for scripts and extension files

[robin-a-meade]

• [x] I have read the CONTRIBUTING guidelines
• [ ] I've had a conversation on the #cli-development Slack channel about this request.

Feature request Follow symlinks in ~/.sdkman/ext and ~/.sdkman/ext.

This will support users who wish to keep scripts and extensions in a dotfiles repo. They wish to create symbolic links in ~/.sdkman/ext and ~/.sdkman/ext pointing to the real files located in their dotfiles repo.