add markdown badges; configure dependabot (#274)

diff --git a/.github/dependabot.yaml b/.github/dependabot.yaml
new file mode 100644
index 0000000..2144819
--- /dev/null
+++ b/.github/dependabot.yaml

@@ -0,0 +1,8 @@
+# Dependabot configuration file.
+version: 2
+
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2637c50..e42e892 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: ci
+name: Dart
 
 on:
   push:
@@ -17,8 +17,10 @@
         sdk: [2.14.0, dev]
 
     steps:
-      - uses: actions/checkout@v2.3.4
-      - uses: dart-lang/setup-dart@v1.2
+      # These are the latest versions of the github actions; dependabot will
+      # send PRs to keep these up-to-date.
+      - uses: actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b
+      - uses: dart-lang/setup-dart@6a218f2413a3e78e9087f638a238f6b40893203d
         with:
           sdk: ${{ matrix.sdk }}
       - run: dart pub get

diff --git a/README.md b/README.md
index dc1dacb..b14069f 100644
--- a/README.md
+++ b/README.md

@@ -1,4 +1,6 @@
-[![CI](https://github.com/google/vector_math.dart/workflows/ci/badge.svg?branch=master)](https://github.com/google/vector_math.dart/actions?query=workflow%3Aci+branch%3Amaster)
+[![Dart](https://github.com/google/vector_math.dart/workflows/ci/badge.svg?branch=master)](https://github.com/google/vector_math.dart/actions?query=workflow%3Aci+branch%3Amaster)
+[![pub package](https://img.shields.io/pub/v/vector_math.svg)](https://pub.dev/packages/vector_math)
+[![package publisher](https://img.shields.io/pub/publisher/vector_math.svg)](https://pub.dev/packages/vector_math/publisher)
 [![Coverage Status](https://coveralls.io/repos/google/vector_math.dart/badge.svg?branch=master)](https://coveralls.io/r/google/vector_math.dart?branch=master)
 
 ## Introduction
@@ -152,13 +154,13 @@
 
 ## Development
 
-To run test cases:
+To run the unit tests:
 
 ```
-~/src/vector_math/> pub run test:test
+~/src/vector_math/> dart test
 ```
 
-To automatically generate the latest version of ```vector_math_64```:
+To automatically generate the latest version of `vector_math_64`:
 
 ```
 ~/src/vector_math/> dart tool/generate_vector_math_64.dart