Table of Contents. Readme readability.

[gordey4doronin]

Hi,

While adding Pretty Print description to the documentation (which is still in progress, I will submit PR later), I've realized it's a bit difficult to navigate through the whole readme/documentation page.

So I added a table of contents. Please check and say what do you think?

Also played around with headers levels (h3 became h4, h4 became h6) to try increase readability for parameters enumerations (for example IgnoreObsoleteProperties, MapType, SchemaFilter, UseFullTypeNamesInSchemaIds etc).

Of course I can revert headers if you don't like how it looks now and leave only table of contents.

P.S. Commits can be squashed if needed.

Regards

[gordey4doronin]

@domaindrivendev Could you please check how readme looks in this PR?
If you like it - I will do a rebase and resolve a conflict.

I also noticed you just released the new version (I got an email notification on some closed PRs);
Unfortunately I totally forgot about Pretty Print documentation description. I will add it soon.

[gordey4doronin]

Rebased f280ebb

[domaindrivendev]

Closing as there's a broader initiative around docs gaining traction with the help of @lockewritesdocs and @heldersepu. See #1053 (comment)