Refactor/typescript header single article

[jtoaha]

Created a refactored-fronted/frontendts folder with aim of having it replace the whole frontend folder once the typescript has been fully converted.

• [x] Added Preact Typescript template
• [x] Copied over assets, css files, and folders for the components,
• [x] Converted Single Article, Header, and App components to typescript
• [x] Updated to latest Typescript version (4.1.5) to deal with compiler error
• [x] Waiting on all converted files to be added before making an official pull request.
• [x] Original Javascript Frontend folder replaced by updated Typescript Frontend Folder

Added in suggested changes from Michael. And it currently, successfully builds with what has been added so far.

[isedwards]

@michaelclapham not sure if you got an email relating to this - would you be happy to have a look through and merge?