Add winget installation note for README.md (#15674)

Adds a note to the ReadMe's installation instructions which describes
why current versions of Terminal are unavailable via winget.

## PR Checklist
- [x] Closes #15663 
- [ ] Tests added/passed
- [ ] Documentation updated
- If checked, please file a pull request on [our docs
repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
- [ ] Schema updated (if necessary)

README.md

@@ -70,6 +70,8 @@ package:
 winget install --id Microsoft.WindowsTerminal -e
 ```
 
+> **Note** Due to a dependency issue, Terminal's current versions cannot be installed via the Windows Package Manager CLI. To install the stable release 1.17 or later, or the Preview release 1.18 or later, please use an alternative installation method.
+
 #### Via Chocolatey (unofficial)
 
 [Chocolatey](https://chocolatey.org) users can download and install the latest