Add PR-BUILD.md and Pull Request Template

.github/PR-BUILD.md

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+## How to test a PR build
+
+Please take into account, that RPCS3 build usually takes some time (about 20 min), so you can't access a build, if a PR was just submitted.
+
+- Open a PR you want to test
+- Scroll to the very bottom and locate "Checks" section
+- Expand all checks
+	You are supposed to see something like this
+	![image](https://user-images.githubusercontent.com/44116740/102790039-f98f6d00-43b5-11eb-9134-2359b732508d.png)
+- Click on **Linux_Build** or **Windows_Build** __Details__
+- Click **View more details on Azure Pipelines** at the very bottom
+	![image](https://user-images.githubusercontent.com/44116740/102790281-45daad00-43b6-11eb-90e7-0fa8c37c31c6.png)
+- Click on *1 artifact produced*
+	![image](https://user-images.githubusercontent.com/44116740/102790526-9a7e2800-43b6-11eb-9925-be1ea1c8bdad.png)
+- Select a build for your OS and click three dots on the right, Click **Download artifacts**
+	![image](https://user-images.githubusercontent.com/44116740/102790636-c9949980-43b6-11eb-9692-1e3ba567b9be.png)
+	
+- Congratulations! You are now downloading RPCS3 build for specific PR.
+
+Please note, that PR builds are not supposed to be stable, because they contain new changesets. 

.github/PULL_REQUEST_TEMPLATE/1-default.md

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+<!-- Please include a summary of the change and which issue is fixed. -->
+
+[How to test this PR](.github/PR-BUILD.md)