[Installation] - Improve Installation for Windows Users

- **What this feature does**:
Windows user should be able to use the dagger binary getting a similar experience to the one proposed for Linux in the docs.
- **What has been changed**: the feature implement a powershell script similar to `install.sh` logic. More specifically I've updated `install.md` and added `install.ps1`

I'm not sure if the  URL `releases.dagger.io` is currently pointing at the content of GH repo or something else so the documented steps may need a review.

Signed-off-by: alefesta <afesta@alfweb.com>

docs/install.md

@@ -35,6 +35,23 @@ You can then install it globally on your system:
 sudo mv ./bin/dagger /usr/local/bin
 ```
 
+## Option 2 (Windows): Run a shell script
+
+Since Dagger repository is currently private, we have to use a workaround
+to be able to run the script and match the latest release.
+This workaround will be removed once the repo will become public.
+To generate a personal access token on GitHub follow the guidelines  at [Create a personal access token](https://docs.github.com/en/github/authenticating-to-github/keeping-your-account-and-data-secure/creating-a-personal-access-token)
+
+From a terminal, run the following command:
+
+```shell
+$personalToken= <INSERT YOUR PERSONAL TOKEN>
+curl https://releases.dagger.io/dagger/install.ps1 -OutFile install.ps1 ; ./install.ps1 -PersonalToken $personalToken; rm install.ps1
+```
+
+We try to move the dagger binary under `C:\Windows\System32` but
+in case use missing the necessary permission we'll save everything under `<your home folder>/dagger`
+
 ## Option 3: Download a binary release
 
 Open your web browser to [the latest release](https://github.com/dagger/dagger/releases/latest).