Add azure pipelines build for CI and PR build previews (#26) [skip ci]

Set up CI with Azure Pipelines [skip ci]

.gitignore

@@ -1,2 +1,3 @@
 node_modules
 coverage
+docs

azure-pipelines.yml

@@ -0,0 +1,78 @@
+trigger:
+- master
+
+pool:
+  vmImage: 'ubuntu-latest'
+
+steps:
+- checkout: self
+  persistCredentials: true
+  clean: true
+
+- script: |
+    echo "##vso[task.setvariable variable=DocsDirectory]$(Build.ArtifactStagingDirectory)"
+  condition: and(succeeded(), in(variables['Build.SourceBranch'], 'refs/heads/master', 'refs/heads/azure-pipelines'))
+  displayName: 'configure publish for CI'
+
+- script: |
+    echo "##vso[task.setvariable variable=DocsDirectory]$(Build.ArtifactStagingDirectory)/pr/$(System.PullRequest.PullRequestNumber)"
+  condition: and(succeeded(), eq(variables['Build.Reason'], 'PullRequest'), variables['System.PullRequest.PullRequestNumber'])
+  displayName: 'configure publish for PR'
+
+- script: |
+    echo "##vso[task.logissue type=error]Pipeline only supported for CI or PR builds"
+    exit 1
+  condition: and(succeeded(), eq(variables['DocsDirectory'], ''))
+  displayName: 'fail invalid build'
+
+- script: |
+    git config user.email "ron.buckton@microsoft.com"
+    git config user.name "Ron Buckton"
+  displayName: 'configure git user'
+
+- task: NodeTool@0
+  inputs:
+    versionSpec: '10.x'
+  displayName: 'Install Node.js'
+
+- script: |
+    npm install
+  displayName: 'npm install'
+
+- script: |
+    gulp build
+  displayName: 'gulp build'
+
+- task: CopyFiles@2
+  inputs:
+    SourceFolder: docs
+    TargetFolder: $(DocsDirectory)
+    OverWrite: true
+  displayName: 'Copy Build Artifacts'
+
+- task: PublishBuildArtifacts@1
+  inputs:
+    PathToPublish: $(Build.ArtifactStagingDirectory)
+    ArtifactName: 'drop'
+    publishLocation: 'Container'
+  displayName: 'Publish Build Artifacts'
+
+- script: |
+    git fetch origin gh-pages
+    git checkout gh-pages --force
+    git clean -fdx
+  displayName: 'checkout gh-pages'
+
+- task: CopyFiles@2
+  inputs:
+    SourceFolder: $(Build.ArtifactStagingDirectory)
+    TargetFolder: $(Build.SourcesDirectory)
+    OverWrite: true
+  displayName: 'Copy built outputs'
+
+- script: |
+    git add --all
+    git status
+    git commit -m "(chore) Publish update to gh-pages"
+    git push origin gh-pages
+  displayName: 'publish gh-pages'