Make it easier to see (and download) artifacts (#3193)

* Much easier way to expose download links in README

The previous instructions would have users go to appveyor and click on the platform and find the "Artifacts" tab and click download. I have added direct links to the download zip files.

* Update artifact location link, and move the section to the top.

* back to direct links. Added ?branch=master&pr=false.

README.md

@@ -7,6 +7,13 @@ The DirectX Shader Compiler project includes a compiler and related tools used t
 
 For more information, see the [Wiki](https://github.com/microsoft/DirectXShaderCompiler/wiki).
 
+## Downloads
+You can download the latest successful build's artifacts (built by Appveyor) for the master branch:
+| Downloads |        |
+|-----------|--------|
+| Windows   | [⬇](https://ci.appveyor.com/api/projects/antiagainst/directxshadercompiler/artifacts/build%2FRelease%2Fdxc-artifacts.zip?branch=master&pr=false&job=image%3A%20Visual%20Studio%202017) |
+| Ubuntu    | [⬇](https://ci.appveyor.com/api/projects/antiagainst/directxshadercompiler/artifacts/build%2Fdxc-artifacts.tar.gz?branch=master&pr=false&job=image%3A%20Ubuntu) |
+
 ## Features and Goals
 
 The starting point of the project is a fork of the [LLVM](http://llvm.org/) and [Clang](http://clang.llvm.org/) projects, modified to accept HLSL and emit a validated container that can be consumed by GPU drivers.
@@ -34,9 +41,6 @@ Binary packages containing the output of this project are available from appveyo
 As an example of community contribution, this project can also target the [SPIR-V](https://www.khronos.org/registry/spir-v/) intermediate representation. Please see the [doc](docs/SPIR-V.rst) for how HLSL features are mapped to SPIR-V, and the [wiki](https://github.com/microsoft/DirectXShaderCompiler/wiki/SPIR%E2%80%90V-CodeGen) page for how to build, use, and contribute to the SPIR-V CodeGen.
 
 ## Building Sources
-
-Note: Instead of building manually, you can download the artifacts built by Appveyor for the latest master branch at [here](https://ci.appveyor.com/project/antiagainst/directxshadercompiler/branch/master/artifacts).
-
 Note: If you intend to build from sources on Linux/macOS, follow [these instructions](docs/DxcOnUnix.rst).
 
 Before you build, you will need to have some additional software installed. This is the most straightforward path - see [Building Sources](https://github.com/microsoft/DirectXShaderCompiler/wiki/Building-Sources) on the Wiki for more options, including Visual Studio 2015 and Ninja support.