Proposal to clearly state this script does not support cross-version migration in README

[yyossy5]

When reading the README, I mistakenly assumed that this script might support cross-version migrations (e.g., CentOS 7 → Oracle Linux 8). However, after checking the available options, I noticed that such functionality was not provided. By further reviewing the script, I understood that it is specifically designed for migrations within the same major version (e.g., CentOS 7 → Oracle Linux 7) and does not support cross-version migrations.

To prevent similar misunderstandings, I propose adding the following clarifications to the README:

1. Clearly State That Cross-Version Migrations Are Not Supported
   This script is intended for migrations within the same major version (e.g., CentOS 7 → Oracle Linux 7) and does not support cross-version migrations (e.g., CentOS 7 → Oracle Linux 8).

2. Provide Guidance for Cross-Version Migration Steps
   For users who wish to perform a cross-version migration, it is recommended to first migrate within the same version using this script (e.g., CentOS 7 → Oracle Linux 7) and subsequently use tools like Leapp to upgrade to a newer version (e.g., Oracle Linux 8).
   (Is this correct? What I actually want to do is convert from CentOS 7 to Oracle Linux 8.)

Adding this clarification will help users better understand the script's purpose and provide proper guidance for cross-version migrations.

Thank you for considering this suggestion.

[yyossy5]

This might be related: #178

[yyossy5]

I found this: https://blogs.oracle.com/scoter/post/upgrade-centos-7-to-oracle-linux-8

Using Leapp, is it possible to migrate directly from CentOS 7 to Oracle Linux 8 without needing the centos2ol.sh script? However, I'm concerned that the Leapp method does not specify the versions before and after the migration. Is it a tool specifically for migrating from CentOS 7 to Oracle Linux 8?