[Feature request] Ability to set the theme in code / Make OssLicensesMenuActivity extendable

My app uses two themes (dark and light). After applying the new theme, I need to apply the new theme dynamically in activities via `setTheme` in `onCreate`. But I can't set the theme in `OssLicensesMenuActivity` via code. Only set statically in the manifest:

```

```

**It would be nice to be able to set the theme in code. Something like this:**

```OssLicensesMenuActivity.setActivityTheme(R.style.AppThemeDark);```

**Or at least make `OssLicensesMenuActivity` not final so it can be extended.**