replace jekyll-get-json with our own generator

[zkamvar]

@maneesha noticed problems with the jekyll-get-json gem that we use in our config to fetch our feeds, but not store them locally:

carpentries.org/_config.yml

Lines 136 to 157 in 8b668b1

	## external data sources
	jekyll_get_json:
	- data: all_badged_people
	json: 'https://feeds.carpentries.org/all_badged_people.json'
	- data: all_past_workshops
	json: 'https://feeds.carpentries.org/all_past_workshops.json'
	- data: all_upcoming_workshops
	json: 'https://feeds.carpentries.org/all_upcoming_workshops.json'
	- data: badges_stats
	json: 'https://feeds.carpentries.org/badges_stats.json'
	- data: community_lessons
	json: 'https://feeds.carpentries.org/community_lessons.json'
	- data: help_wanted_issues
	json: 'https://feeds.carpentries.org/help_wanted_issues.json'
	- data: newsletter
	json: 'https://feeds.carpentries.org/newsletter.json'
	- data: members
	json: 'https://feeds.carpentries.org/all_public_memberships.json'
	- data: all_trainers
	json: 'https://feeds.carpentries.org/all_trainers.json'
	- data: all_maintainers
	json: 'https://feeds.carpentries.org/all_maintainers.json'

In essence, the gem fails to fetch the JSON on her machine, but it fails silently. We spent an hour trying to debug it, but to no avail. I asked for a solution on Mastodon and Scott Chamberlain suggested to use a Generator to port the Gem into our website instead of relying on a third-party gem.

Info on Generators: https://jekyllrb.com/docs/plugins/generators/
Link to original gem: https://github.com/brockfanning/jekyll-get-json/blob/master/lib/jekyll-get-json/converter.rb

[maneesha]

Closing this not relevant to the new website.