[FEATURE REQUEST] Expand environment variables in custom install arguments

### Please confirm these before moving forward. - [x] I have searched for my feature proposal and have not found a work-in-progress/duplicate/resolved/discarded issue. - [x] This proposal is a completely new feature. If you want to suggest an improvement or an enhancement, please use [this template](https://github.com/Devolutions/UniGetUI/issues/new?labels=enhancement&projects=&template=enhancement-improvement.yml&title=%5BENHANCEMENT%5D+%28Enter+your+description+here%29). ### Describe the new feature I'm using UniGetUI "installation options" to override the location of apps installed, e.g., use `--location C:\my\path\app` for WinGet. These overrides are stored in app profiles configs, so far so good. But I'd like those app profiles to be portable across machines, so would like to be able to use environment variables in paths that would resolve to differnt paths on different machines For that it would help if UniGetUIsupported environment variable expansion in its interface so I could enter `--location <SystemDrive>my\path\app` and UniGetUI would convert `<SystemDrive>` into `C:\` and pass the results to winget-cli (FYI, I've also asked Winget-cli to do a similar thing https://github.com/microsoft/winget-cli/issues/6388, though it feels like more of a frontend's job? Similar to how in your actual shell you'd add this env var according to the shell rules to expand and pass to the cli the expanded variant?) ### Describe how this new feature could help users Would reduce the amount of machine-specific customization required, increasing portability of UniGetUI app bundles/configs