dart:io APPEND field should be marked as const in Dart API Spec

[iarkh]

dart:io APPEND Spec reads:

APPEND = FileMode.APPEND
The mode for opening a file for reading and writing to the end of it. The file is created if it does not already exist.

It should be marked as const because actually it's a constant and cannot be changed.
So, description should look loke one for FileMode.APPEND field:
dynamic APPEND = **const** FileMode._internal(2)
See here: https://api.dartlang.org/stable/1.24.3/dart-io/APPEND-constant.html

Some other fields from dart:io Constants section in the Spec are also not marked const: READ, WRITE, WRITE_ONLY, WRITE_ONLY_APPEND.

[floitschG]

Marking as a dartdoc issue.
The constant itself is const.

const APPEND = FileMode.APPEND;

The const in front of it makes the variable constant.
However, dartdoc doesn't show this in the documentation.

[floitschG]

This issue was moved to dart-lang/dartdoc#1576