Show the CLI reading its template from stdin in the README, the usage and the decisions, file the stdin change under Unreleased, and leave item 129 the library's half

CHANGELOG.md

@@ -12,7 +12,7 @@ replacement, and each removed path, column or flag.
   `{/city[Oslo]..country.name}` renders `Norway`, and `.` after it steps down again,
   drawing afresh. `New` refuses a `..` naming anything but the parent table, and a
   selector after a `..`.
-- A path, given to `Fake` or the CLI or referenced in a template, may not read into a
+- A path, given to `Fake` or referenced in a template, may not read into a
   level carrying a `repeat`, and `List` advertises no such path: where `x` carries
   `"repeat": 3`, `Fake("x.a")` fails naming the level `x`, and `Fake("x")` renders it
   whole.
@@ -27,6 +27,11 @@ replacement, and each removed path, column or flag.
   operand: `{/misc.coordinate.lat as lat}{calc(lat * 60)}`. What `New` refuses is listed
   under [Names](README.md#names).
 - First release: the CLI, the library and the shipped data set.
+- The CLI renders the template piped to its stdin, `echo -n '{/sv_SE.person} hihi' |
+  fejkdata`, and takes no path or template as an argument. One newline ending stdin is
+  dropped, and so is the whitespace around a JSON template. A template of one reference
+  alone, `{/users}`, is the record `users` under `--format`. An argument, or nothing
+  piped in, exits 2.
 - Table categories: a category JSON naming a `rows` TSV beside it, with the options
   `key`, `name`, `weight` and `parent`; a path selects a row by key or name,
   `misc.territory[SE]`, and descends to a linked table by name, one path drawing each