[Suggestion] Add keyboard opacity slider

[maciekprzysowa]

Your system information

• Steam client version: stable
• SteamOS version: stable
• Opted into Steam client beta?: No
• Opted into SteamOS beta?: No
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

For games in which you can enter text (i.e. having built-in text chat) it would be extremely helpful to see the text that is being input. Currently, there is no opacity setting for keyboard, and it's position can't be moved (always sticky to bottom of screen). It would be beneficial to add opacity slider to the settings (defaulting to 100, so no regression from the UI perspective here) that would allow users to reduce it, hence giving way to see the focused field / input text.

Steps for reproducing this issue:

1. Focus field on bottom of the screen
2. Show keyboard
3. The field is not visible, so you don't know what you're typing