Sharing: Text hidden behind the keyboard when large text is selected.

When using the option to share from one app to Simplenote and a large portion of text is added, the text becomes trapped behind the keyboard and there is no way to edit the section that overflows.

### Expected

I'd expect to be able to scroll the full way down to edit the full text.

### Observed

The text is hidden by the keyboard and can't be editable.

### Reproduced

> 1. Go to a different app, like Instapaper or News.
> 2. Tap on the share icon and select the option to Share to Simplenote.
> 3. Make sure the text box has large amounts of text, or paste a large portion of text in the box.
> 4. You will see the error if you try to scroll to the bottom of the screen.


***(Optional)*** If you reproduced the bug on a specific device, please replace DEVICE_MAKE, DEVICE_MODEL, IOS_VERSION, and APP_VERSION below with the details for that device. If you reproduced the bug on multiple devices, please add a row for each device.

Make|Model|iOS Version|App Version
-|-|-|-
iPhone|X|iOS 14.2|4.27

User reported in 3499081-zen

Start by reproducing the share-to-Simplenote flow on iOS with a large text selection, then inspect the screen responsible for editing the shared text and keyboard behavior. Done means the full text remains scrollable and the overflow can be edited while the keyboard is shown.

Written by the indexing model from the issue text.