Copy docs into Zeek repo directly

This is based on commit 99e6942efec5feff50523f6b2a1f5868f19ab638 from the
zeek-docs repo.

doc/components/index.rst

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+
+=============
+Subcomponents
+=============
+
+To find documentation for the various subcomponents of Zeek, see their
+respective GitHub repositories or documentation:
+
+* `Spicy <https://docs.zeek.org/projects/spicy>`__
+  - C++ parser generator for dissecting protocols & files.
+* `BinPAC <https://github.com/zeek/binpac>`__
+  - A protocol parser generator
+* `ZeekControl <https://github.com/zeek/zeekctl>`__
+  - Interactive Zeek management shell
+* `Zeek-Aux <https://github.com/zeek/zeek-aux>`__
+  - Small auxiliary tools for Zeek
+* `BTest <https://github.com/zeek/btest>`__
+  - A system testing framework
+* `Capstats <https://github.com/zeek/capstats>`__
+  - Command-line packet statistic tool
+* `PySubnetTree <https://github.com/zeek/pysubnettree>`__
+  - Python module for CIDR lookups
+* `trace-summary <https://github.com/zeek/trace-summary>`__
+  - Script for generating break-downs of network traffic
+* `Broker <https://github.com/zeek/broker>`__
+  - Zeek's Messaging Library
+  - `(Docs) <https://docs.zeek.org/projects/broker>`__
+* `Package Manager <https://github.com/zeek/package-manager>`__
+  - A package manager for Zeek
+  - `(Docs) <https://docs.zeek.org/projects/package-manager>`__
+* `Paraglob <https://github.com/zeek/paraglob>`__
+  - A pattern matching data structure for Zeek.
+  - `(Docs) <https://github.com/zeek/paraglob/blob/master/README.md>`__