Add color to error formatting (#746)

* Add color to error formatting

* Apply suggestions from code review

Co-authored-by: Daniel Chao <daniel.h.chao@gmail.com>

* Address reviewer comments

* Apply suggestions from code review

Co-authored-by: Daniel Chao <daniel.h.chao@gmail.com>

* Define style choices as operations on formatter (abandon semantic API)

* Adjust margin styling

* Review feedback

* Documentation nits

---------

Co-authored-by: Daniel Chao <daniel.h.chao@gmail.com>

docs/modules/pkl-cli/partials/cli-common-options.adoc

@@ -19,6 +19,19 @@ Patterns are matched against the beginning of resource URIs.
 At least one pattern needs to match for a resource to be readable.
 ====
 
+[[color]]
+.--color
+[%collapsible]
+====
+Default: `auto` +
+When to format messages with ANSI color codes.
+Possible values:
+
+- `"never"`: Never format
+- `"auto"`: Format if `stdin`, `stdout`, or `stderr` are connected to a console.
+- `"always"`: Always format
+====
+
 [[cache-dir]]
 .--cache-dir
 [%collapsible]