Lua filters: load module `pandoc` before calling `init.lua` (#5287)

The file `init.lua` in pandoc's data directory is run as part of
pandoc's Lua initialization process. Previously, the `pandoc` module was
loaded in `init.lua`, and the structure for marshaling was set-up after.
This allowed simple patching of element marshaling, but made using
`init.lua` more difficult:

  - it encouraged mixing essential initialization with user-defined
    customization;

  - upstream changes to init.lua had to be merged manually;

  - accidentally breaking marshaling by removing required modules was
    possible;

Instead, all required modules are now loaded before calling `init.lua`.
The file can be used entirely for user customization. Patching
marshaling functions, while discouraged, is still possible via the
`debug` module.

0 files changed, 0 insertions, 0 deletions