feat(install): add Windows PowerShell installer and copy buttons on site

Add install.ps1 mirroring install.sh for Windows: arch detection,
release zip download, binary extraction, user PATH update.

- copy install.ps1 to site public/ at build time (copy-install.mjs)
- serve /install.ps1 with text/plain Content-Type (vercel.json)
- add PowerShell one-liner to install page and README
- bump install.ps1 default version in bump_version.sh
- add CopyButton component next to every install command line

README.md

@@ -173,7 +173,13 @@ curl --proto '=https' --tlsv1.2 -sSLf https://termscp.rs/install.sh | sh
 
 > ❗ MacOs installation requires [Homebrew](https://brew.sh/), otherwise the Rust compiler will be installed
 
-while if you're a Windows user, you can install termscp with [Chocolatey](https://chocolatey.org/):
+if you're a Windows user, you can install termscp from PowerShell with a single command:
+
+```ps
+irm https://termscp.rs/install.ps1 | iex
+```
+
+or, alternatively, with [Chocolatey](https://chocolatey.org/):
 
 ```ps
 choco install termscp