Add design log

Author: TravisCardwell

project/log/20200822-design.md

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+# `queue-sheet-haskell` Design Log
+
+Author
+: Travis Cardwell
+
+Date
+: 2020-08-22
+
+## Sharing
+
+Queue sheets are convenient for tracking progress through conference videos
+and university lectures.  I would like to share those that I make with others,
+and I made the following major design changes to make the program easier for
+multiple people to work with:
+
+* Support was added for a "default" section, for queue sheets that do not need
+  sections.  One can specify the queue list as a top-level array to simplify
+  queue files in this case.
+* Support was added for importing other queue files, either inheriting
+  sections or overriding them.  This allows users to easily create a custom
+  queue sheet that includes queues defined in separate files.
+* Support was added for associating URLS with queues as well as queue items.
+  This makes it easy for users to easily locate the media indexed by a queue.
+
+## User-Defined Tags
+
+Support was added for user-defined tags, which can be handled in any way that
+the user wants in the template.  This simplifies the design of the program yet
+makes it more flexible.
+
+The initial design used a special "split" flag, intended to be used to display
+items on separate lines.  This flag has been removed, as the same
+functionality can be implemented using a "split" tag.