RPM Outpost Discord Versions Save

What's new from the last release:

• Use yum if dnf isn't available
• Use curl if wget isn't available
• Support discord PTB (that is, indev): use create-package.sh ptb
• Dependency requirements fixed

I began to support CentOS but couldn't achieve it because the CentOS version of libcxx is too old for the recent discord updates.

• create_package.sh now works on OpenSUSE too!
• More rpm-based distributions could be added later.
• A few bugfixes since the previous release

• One script to install both canary and stable
• Cleaner and colored output
• Can install the package right after building it
• Discord canary and stable are installed in separate locations, so they can coexist on the same machine.
• All bugs fixed