Fix tutorial fileTemplates

Our templates were out of date, and our `install.sh` script doesn't work any more.
Replaced with an IDE-produced zip file that the IDE is willing to import.

Replaces `Layout Runner (ViewBinding)` with `Android Screen (ViewBinding)`:

```kotlin
package ${PACKAGE_NAME}

import com.squareup.workflow1.ui.AndroidScreen
import com.squareup.workflow1.ui.ScreenViewFactory
import com.squareup.workflow1.ui.ScreenViewRunner
import com.squareup.workflow1.ui.ViewEnvironment
import com.squareup.workflow1.ui.WorkflowUiExperimentalApi

@OptIn(WorkflowUiExperimentalApi::class)
data class $Name(
  // TODO: add properties needed to update $VIEW_BINDING_TYPE
) : AndroidScreen<$Name> {

  override val viewFactory =
    ScreenViewFactory.fromViewBinding($VIEW_BINDING_TYPE::inflate, ::${Name}Runner)
}

@OptIn(WorkflowUiExperimentalApi::class)
private class ${Name}Runner(
  private val viewBinding: $VIEW_BINDING_TYPE
) : ScreenViewRunner<$Name> {

  override fun showRendering(
    rendering: $Name,
    environment: ViewEnvironment
  ) {
    TODO("Update viewBinding from rendering")
  }
}
```

Author: rjrjr

README-templates.md

@@ -0,0 +1,8 @@
+# File Templates
+
+`workflow-file-templates.zip` can be imported into Android Studio / IntelliJ IDEA to add a few Workflow-specific file templates, via _File > Manage IDE Settings > Import Settings…_.
+
+To update the templates:
+
+* edit them in the IDE (_Settings > Editor > File and Code Templates_)
+* export them (_File > Manage IDE Settings > Import Settings…_), taking care to clear every checkbox except that for File Templates.