Add Icelandic layout

[vjpbd]

Checklist

• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

It would be nice to add the Icelandic keyboard layout (wikipedia) to the app.

Why do you want this feature?

Specific Icelandic letter are missing from other keyboard layouts.
In some other keyboard apps, the Icelandic letter "Ð ð" is available under "d" and the Icelandic letter "Þ þ" is available under "t" on their English QWERTY layout but this is not the case in the Fossify Keyboard app.

Additional information

No response