Update Documentation

- added screenshot
- added doc export using pandoc to html and pdf

doc/tools/noexport-subtrees.lua

@@ -0,0 +1,61 @@
+--[[
+Remove all subtrees whose headlines contain class `noexport`.
+
+License:   MIT
+Copyright: © Albert Krewinkel
+]]
+
+-- pandoc.utils.make_sections exists since pandoc 2.8
+PANDOC_VERSION:must_be_at_least {2,8}
+
+local utils = require 'pandoc.utils'
+
+-- Returns true iff a div is a section div.
+local function is_section_div (div)
+  return div.t == 'Div'
+    and div.classes[1] == 'section'
+    and div.attributes.number
+end
+
+-- Returns the header element of a section, or nil if the argument is not a
+-- section.
+local function section_header (div)
+  if not div.t == 'Div' then return nil end
+  local header = div.content and div.content[1]
+  local is_header = is_section_div(div)
+    and header
+    and header.t == 'Header'
+  return is_header and header or nil
+end
+
+--- Remove remaining section divs
+local function flatten_sections (div)
+  local header = section_header(div)
+  if not header then
+    return nil
+  else
+    header.identifier = div.identifier
+    div.content[1] = header
+    return div.content
+  end
+end
+
+function drop_noexport_sections (div)
+  if div.classes:includes('noexport') then
+    return {}
+  end
+end
+
+--- Setup the document for further processing by wrapping all
+--- sections in Div elements.
+function setup_document (doc)
+  local sections = utils.make_sections(false, nil, doc.blocks)
+  return pandoc.Pandoc(sections, doc.meta)
+end
+
+return {
+  {Pandoc = setup_document},
+  {Div = drop_noexport_sections},
+  {Div = flatten_sections}
+}
+