docs(readme): clarify install for v2 vs v3 alpha (#5268)

* docs(readme): clarify install for v2 vs v3 alpha

Adds a small two-row table under "Getting Started" so readers can see
at a glance which version they want to install: v2 (stable) for
production use, or v3 (alpha) for the next-generation build. The rest
of the README — sponsors image, badges, FAQ, etc. — is unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Update README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

README.md

@@ -91,7 +91,14 @@ it before creating an enhancement request.
 
 ## Getting Started
 
-The installation instructions are on the [official website](https://wails.io/docs/gettingstarted/installation).
+Wails has two active versions:
+
+| Version | Status | Install | Docs |
+|---|---|---|---|
+| v2 | Stable | `go install github.com/wailsapp/wails/v2/cmd/wails@latest` | [wails.io](https://wails.io/) |
+| v3 | Alpha | `go install github.com/wailsapp/wails/v3/cmd/wails3@latest` | [v3.wails.io](https://v3.wails.io/) |
+
+Full installation instructions are available for [v2](https://wails.io/docs/gettingstarted/installation) and [v3](https://v3.wails.io).
 
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