Explanation about symbolic link

[miurahr]

Is your feature request related to a problem? Please describe.

v0.5b3 supports symbolic link archive wihch is as same as p7zip does.
A link extension is not implemented by original 7zip .

Describe the solution you'd like

We need to explain a situation and limitation on README and documentation.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days

[miurahr]

Updated.