103 how to edit mode

[BenGamma]

WIP on the how to edit mode.

Main work done is :

• create a EditHowto component
• move howto form from CreateHowTo to a Common folder so it can be used by Create & Edit howto pages
• add props to howtoForm component : onSubmit(), parentType & formValues
• inject existing text how-to values from store in the edit form
• inject cover_image , step images, files and tags to edit form
• create display mechanism for images

Known todo :

• show existing files in the files inputs. @chrismclarke do you have an idea of how to do that ? After a quick search I found the custom store section in uppy doc, would be something like that ?
• allow only creator & admin to modify the how-to
• prevent when edit, loosing the preLine on howto description and step text block
• display upload modal or at least any visual feedback from submit
• redirect to how-to page after upload
• add breadcrumb on top

[chrismclarke]

For the most part looks good, requested on small change in-line, and will look into the upload files now