Update readme

Author: chelnak

README.md

@@ -1,6 +1,27 @@
 # Azure Pipelines tasks
 
-TODO:
-* Update readme
-* Yaml build
-* Test runner
+This repository contains custom Azure Pipelines tasks.
+
+## Creating new tasks
+
+When creating a new task follow the [official documentation](https://docs.microsoft.com/en-us/azure/devops/extend/develop/add-build-task?view=azure-devops).
+
+You can also use the [schema](https://github.com/Microsoft/azure-pipelines-task-lib/blob/master/tasks.schema.json) provided by Microsoft when building your `task.json` definition.
+
+If your task has external dependencies ensure that you include a `dependency.json` file in the root of the task directory. The following dependency sources are supported:
+
+* GitHub
+* PowerShell Gallery
+* NuGet
+
+Use [this file](tasks\EnvironmentConfiguration\dependency.json) as a reference when building your `dependency.json`.
+
+## Building locally
+
+```PowerShell
+./BuildTask.ps1 -TaskRoot tasks/MyTask
+```
+
+## Building in Azure DevOps
+
+Create an `azure-pipelines.yml` in the root of your task directory and reference `azure-pipelines.template.json` from the root of the repository. Use [this file](tasks\EnvironmentConfiguration\azure-pipelines.yml) as a reference.