Update CHANGELOG for Platform.ansiSupported

CHANGELOG.md

 ## 1.23.0
 
 ### Language
 * Allow using URI strings in `part of` declarations to refer to the
   importing library.
 
 ### Core library changes
 * `dart:core`: Added `Uri.isScheme` function to check the scheme of a URI.
    Example: `uri.isScheme("http")`. Ignores case when comparing.
 * `dart:core`: Make `UriData.parse` validate its input better.
   If the data is base-64 encoded, the data is normalized wrt.
   alphabet and padding, and it contains invalid base-64 data,
   parsing fails. Also normalizes non-base-64 data.
 * `dart:io`: Added functions `File.lastAccessed`, `File.lastAccessedSync`,
   `File.setLastModified`, `File.setLastModifiedSync`, `File.setLastAccessed`,
   and `File.setLastAccessedSync`.
+* `dart:io`: Added `Platform.ansiSupported`.
 
 ### Dart VM
 * Calls to `print()` and `Stdout.write*()` now correctly print unicode
   characters to the console on Windows. Calls to `Stdout.add*()` behave as
   before.
 
 ### Tool changes
 
 * Analysis
 
   * The `dartanalyzer` now follows the same rules as the analysis server to find an analysis options file,
     stopping when an analysis options file is found:
     * Search up the directory hierarchy looking for an analysis options file.
-    * If analyzing a project referencing the [Flutter](https://flutter.io/) package, then use the 
+    * If analyzing a project referencing the [Flutter](https://flutter.io/) package, then use the
       [default Flutter analysis options](https://github.com/flutter/flutter/blob/master/packages/flutter/lib/analysis_options_user.yaml)
       found in `package:flutter`.
     * If in a Bazel workspace, then use the analysis options in `package:dart.analysis_options/default.yaml` if it exists.
     * Use the default analysis options rules.
   * In addition, specific to `dartanalyzer`:
-    * an analysis options file can be specified on the command line via `--options` 
+    * an analysis options file can be specified on the command line via `--options`
       and that file will be used instead of searching for an analysis options file.
-    * any analysis option specified on the command line (e.g. `--strong` or `--no-strong`) 
+    * any analysis option specified on the command line (e.g. `--strong` or `--no-strong`)
       takes precedence over any corresponding value specified in the analysis options file.
 
 
 ## 1.22.0
 
 ### Language
 
   * Breaking change: ['Generalized tear-offs'](https://github.com/gbracha/generalizedTearOffs/blob/master/proposal.md)
     are no longer supported, and will cause errors. We updated the language spec
     and added warnings in 1.21, and are now taking the last step to fully
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     they will keep the Dart process alive until they time out. This fixes the
     handling of persistent connections. Previously, the client would shut down
     immediately after a request.
 
   * **Breaking change:** `HttpServer` no longer compresses all traffic by
     default. The new `autoCompress` property can be set to `true` to re-enable
     compression.
 
 * `dart:isolate`: `Isolate.spawnUri` added the optional `packageRoot` argument,
   which controls how it resolves `package:` URIs.