[rebber] Lots of corrections and improvements

[StaloneLab]

These are the last changes until next release; I plan on publishing a major version of rebber, which requires the following to be solved:

• add mhchem (KaTeX: add mchem #359): done and merged;
• array improvements (rebber: array improvements #374): done and merged;
• array issue (rebber: array issue #375): done and merged;
• avoid spoiler in spoiler ([rebber] Avoid spoiler in spoiler ? #280): done, first in this PR;
• allow to disable custom tokenizers (for Ignore images for the signature (message footer)  #313): done, second in this PR but not sure it solves the issue;
• add options to zmarkdown's LaTeX endpoint ([rebber&zmarkdown] add additional options to latex-document enpoint #283 only): done, third in this PR;
• send codeblocks to appendices (rebber: codeblocks in footnotes are not well parsed by latex #299): done and merged;
• add a \ping command (none): done, fourth in this PR;
• add missing dependencies to rebber ([rebber] Missing dependencies in package.json #384): done, fifth in this PR.

We will be able to publish soon enough, now everything is done.

[artragis]

We could add some changelogs.

• in rebber:
  • add missing dependency
  • fix linkReference default macro (uses hyperref from hypertext package instead of bare ref)
• in rebber-plugins :
  • fix grid-table/align interraction
  • add ping command
  • fix appendix management
  • avoid imbrication of spoilers
• in zmarkdown:
  • push codes that were inside footnote into appendix
  • add parameter in endpoints

[vhf]

LGTM