Display and style the Table of Contents for posts where it's enabled

[monacodelisa]

Describe the solution you'd like
On Hashnode there is an option to display Table of Contents for each blog.
Working on this issue requires the following:

• investigate why the table of contents is not showing, possibly it requires an additional GraphQL query
• perform a check to see if the table of contents is enabled
• conditionally display the table of contents in the post-detais component if it is enabled, to be placed below the cover image
• style the table of contents - we want to use an expansion panel for it
• there are various ways to achieve that in this app version the way to do it is by utilizing components provided by PrimeNG
• discuss your proposed solution, try and test different options
• table of contents may be a partial component if it makes sense

Additional context