Add freecodecamp support about zimfarm

[benoit74]

Small points that needs to be confirmed :

• we support only the all command of fcc2zim (individual commands fetch, prebuild, zim) makes no sense in Zimfarm
• we need a new platform in addition to the new offliner, in order to limit the number of tasks for fcc2zim per worker
• we limit to 1 fcc2zim task per worker for now (this is not managed in this repo but better ask the question now)
• output flag is not standard: "outpath" instead of "output"
• there is no support for the JSON stat file in fcc2zim (for now)

[rgaudin]

* we support only the `all` command of `fcc2zim` (individual commands `fetch`, `prebuild`, `zim`) makes no sense in Zimfarm

Yes ; ZF doesn't care about scraper internals. We want to be able to supply the list of courses, the metadata and get a ZIM.

* we need a new platform in addition to the new offliner, in order to limit the number of tasks for fcc2zim per worker
* we limit to 1 fcc2zim task per worker for now (this is not managed in this repo but better ask the question now)

No. Those are created only if we encounter issues.

* output flag is not standard: "outpath" instead of "output"

Right.

* there is no support for the JSON stat file in fcc2zim (for now)

Right.

[benoit74]

This task is not possible to complete, work on openzim/freecodecamp#11 needs to be finished (at least first point on CLI parameters) for this task to make sense (otherwise no one but few devs will be able to create recipes for this scraper)

[benoit74]

I pushed some WIP code on the branch add_fcc (https://github.com/openzim/zimfarm/tree/add_fcc). Probably mostly ready except Flags / CLI parameters