rev to 2.5.0 and prep to publish (#267)

switch to using package:dart_flutter_team_lints (#247)

* switch to using package:dart_flutter_team_lints

* address example lints

* require dart 2.19

* update action config

added package topics to the pubspec file (#242)

Suggest command based on aliases (#235)

blast_repo fixes (#230)

* blast_repo fixes

auto-publish

* publish from master

prep to publish 2.3.1 (#218)

Add ability to group commands by category in usage (#202)

To enable flutter/flutter#83706

Formatting is loosely based on what `Brew` does, and open to suggestions.  Existing tests are unchanged.

Example (all displayed commands categorized):
<img width="669" alt="Screenshot 2021-07-23 at 16 22 40" src="https://user-images.githubusercontent.com/6655696/126796093-e8652385-c3d7-4600-83b1-76852ab46ea4.png">

show similar commands with an edit distance of 2 or less (#206)

Fixes #201

Uses the Optimal string alignment distance algorithm to compute edit distance, which allows for additions, removals, substitutions, and swaps - all as 1 cost operations.

Suggests any commands within an edit distance of <=2 by default, which is configurable. You can set it to 0 to disable the feature.

fix a null assertion error when there are missing mandatory args in c…

…ommands (#199)

Fixes https://github.com/dart-lang/args/issues/197

The 2nd argument to ArgParserException is supposed to be the command chain that it was parsed from and not the option (note this is handled separately as well) - this was causing the command runner to throw a null assertion error later on by passing the name of the mandatory option as the command name, which doesn't exist as a command.

clean up the sdk constraint and dep overrides (#192)