Copy docs into Zeek repo directly

This is based on commit 2731def9159247e6da8a3191783c89683363689c from the
zeek-docs repo.

doc/ext/literal-emph.py

@@ -0,0 +1,41 @@
+import re
+
+import sphinx
+from docutils import nodes
+
+# This extension adds a 'literal-emph' directive that operates the same
+# as the 'code-block' directive except that it additionally understands
+# the **strong emphasis** markup, allowing custom rendering of it to be
+# substituted in the final literal block (e.g. HTML adds <strong> elements).
+# Adding " (no-emph)" to the end of a line within the 'literal-emph' content
+# disables substitutions for that line.
+
+
+class LiteralEmphNode(nodes.General, nodes.Element):
+    pass
+
+
+class LiteralEmph(sphinx.directives.code.CodeBlock):
+    def run(self):
+        node = LiteralEmphNode()
+        node += super().run()
+        return [node]
+
+
+def visit_litemph_node(self, node):
+    pass
+
+
+def depart_litemph_node(self, node):
+    text = self.body[-1]
+    text = re.sub(r"\*\*(.*?)\*\*(?!.* \(no-emph\)\n)", r"<strong>\1</strong>", text)
+    text = re.sub(r"(.*) \(no-emph\)\n", r"\1\n", text)
+    self.body[-1] = text
+
+
+def setup(app):
+    app.add_directive("literal-emph", LiteralEmph)
+    app.add_node(LiteralEmphNode, html=(visit_litemph_node, depart_litemph_node))
+    return {
+        "parallel_read_safe": True,
+    }