Feat: `Capture` == `Edit` Mode Screen + Functionality

[nelsonic]

As noted in dwyl/mvp#214 our goal is to have a totally separate Edit page
so that the person editing the item can fully focus on what they are doing without any distractions.
What is not covered in that issue is that the screen for initial Capture is the same
and all we will be doing is pre-populating it with item.text and tags when it's in Edit Mode.

Some of this work is captured by @SimonLab in: multiline Flutter TextField #303

Todo

• Create Wireframes in Figma for this.