Adds simple localization features

[bitschmidty]

Changes:

• on individual newsletter pages, show available translations, if they exist
• filters on homepage for only english posts
• filters on newsletter page for english posts
• supports language additions
• small fix to newsletter layout html

Notes:

• translations will be located in _posts/[language-code]/newsletters/
• only handles newsletter types for now
• simple language codes (en, ja) for selecting translations. can consider flags or other visuals as well.

Testing:

• add a '_posts/ja/newslettes/2019-10-23-newsletter-ja.md'
• see example ja newsletter here: https://github.com/cryptogarageinc/bitcoinops.github.io/blob/newsletter-69/_posts/ja/newsletters/2019-10-23-newsletter-ja.md

[jnewbery]

ACK 009fd1f. This seems fine for a low-key rollout of localized newsletters.

If we continue to get japanese and other language translations, we could:

• add flags/graphics/drop-down menu to make this a bit more pleasing on the eye
• add a localized https://bitcoinops.org/<code>/newsletters/ page so international readers have a place to find all newsletters translated to their language
• add documentation/contrib scripts to make it easier for people to contribute translations.

Thanks for doing this @bitschmidty ! And thanks for handling everything with CG.

[bitschmidty]

Rebased and pushed a commit which filters out non english posts from the existing feed.xml

We should also consider adding language specific feeds in the future.

[bitschmidty]

Created #251 to track non blocking suggestions to localization in the future

[jnewbery]

Did you copy the base feed.xml from somewhere? (I would have guessed here: https://github.com/jekyll/jekyll-feed/blob/master/lib/jekyll-feed/feed.xml but it seems like there are some differences). If so, can you split add feed.xml template which filters for english only into two commits:

• the first adds the unaltered feed.xml file, so reviewers can use it to generate the feed and verify that there are no differences from master.
• the second makes your modifications to feed.xml

[bitschmidty]

Split commits for the feed into two:

1. template xml file from 0.10.0 of the jekyll-feed plugin (our current version)
2. tweak to the template file for filtering on english language only

[harding]

Concept ACK. One bug (need to also filter /en/publications) and one style suggestion. Thanks, @bitschmidty!

Tested by builiding site with and without this PR as is, then diffing static HTML. Then doing that again with the suggested translation on top of this PR. Also browsed a local preview of the test site with the suggested translation. Reviewed code.

[jnewbery]

ACK 560573f.

Thanks for splitting out the feed change into two commits. I've tested the following:

• with just the first commit (add jekyll-feed v 0.10.0 feed template file), there are only whitespace changes
• with the first commit and sample japanese/other language posts, those posts are included in the feed
• with the first commit, sample japanese/other language posts and the second commit (filter xml feed to english language only), the feed is the same as master except for whitespace. All non-english posts are filtered out.

Once you've addressed @harding's feedback, this is ready for merge.

[bitschmidty]

Pushed 2 commits to address feedback from @jnewbery and @harding . Thanks for the review feedback as well as outlining your testing approaches!

[harding]

Tested ACK ba22ddd Thanks!

[jnewbery]

ACK ba22ddd

[jnewbery]

I've squashed the two fixup commits into the relevant commits. Merging now.

Thanks for delivering this, @bitschmidty !