fix pps documentation of ghost

[n-osborne]

This PR add support for the documentation of ghost declarations. Gospel preprocessor should now accept every interleaving of ghost declaration, with and without specification and with or without spaces between these items. Spaces are checked to contains not more than one end of the line character when necessary. Decision has been made (but can obviously been discussed) to support documentation between a ghost declaration and its specification with no constraints on the space in between. (See tests added in the first commit for examples)

Fixes #324

[shym]

I updated this PR with one large modification. Now determining whether space should separate two consecutive items (aka be considered Large) is using data from the lexer (which rules were applied) to handle possibly-nested comments and contained strings properly.

On the way, two minor updates:

• a rebase on main,
• reindenting (two spaces, for consistency).

[shym]

I just force-pushed an update that only fixes a few typos in a commit message. I’ll merge if CI is happy.