Chore: Tidy UI/UX of Adding and Editing tags

[nelsonic]

At present we have the basic tags UI working in the MVP: https://mvp.fly.dev 🎉 (thanks @SimonLab!)

We need to tidy up the UI/UX a little before requesting feedback dwyl/mvp#140 as the layout is clearly a little "off".

Todo

• Add tags label in front of the tags input field to make it clearer. (we can test this later)
• Left-align bot the Tags label and the tags input field
• Match the tags input to the item.text above (light grey)
• Place the save button on the same line/row as the tags input to avoid wasting vertical space
• Float the save button to the left

Apply these same styles to the edit mode.