resolves #522 upgrade to Asciidoctor.js 2

• upgrade to Asciidoctor.js 2.2.x
• change Asciidoctor.js package import from asciidoctor.js to @asciidoctor/core
• change Opal package import from opal-runtime to asciidoctor-opal-runtime
• allow use of newer patch versions of Asciidoctor.js 2.2.x (via dependency spec ~2.2.0)
• add convert_ prefix to node handler methods in extended converter
• update assertions for Asciidoctor.js behavior
  • max include depth warning
  • nested macro in footnote
  • preserve trailing spaces on non-AsciiDoc include file
  • preserve leading and trailing empty lines in AsciiDoc include file
  • implicit source block when source-language is set
  • docrole renamed to role on Document
• fix printing of stacktrace in CLI
• invert assertion for empty stem block; resolves #663 (closed)

mentioned in merge request !423 (closed)

added 3 commits

• 1c8d2f11...670064ff - 2 commits from branch antora:master
• bd6b34b1 - upgrade to Asciidoctor.js 2

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added 7 commits

• bd6b34b1...b97a7748 - 6 commits from branch antora:master
• 15469cb2 - upgrade to Asciidoctor.js 2

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Before merging, we'll need a new Asciidoctor.js release that includes the fix in Asciidoctor for this issue: https://github.com/asciidoctor/asciidoctor/issues/3997

added 15 commits

• 15469cb2...bee8deb8 - 14 commits from branch antora:master
• 8d369ddb - upgrade to Asciidoctor.js 2

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added 12 commits

• 8d369ddb...6a48855e - 11 commits from branch antora:master
• bb543d44 - upgrade to Asciidoctor.js 2

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added 1 commit

• a0c1dd30 - upgrade to Asciidoctor.js 2

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changed the description

added 1 commit

• 82c8e14b - resolves #522 (closed) upgrade to Asciidoctor.js 2

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mentioned in commit 325a440f

merged