Update issue template with performance data

Add instructions for capturing performance data, which is useful for
identifying and fixing perf related issues.

issue_template.md

@@ -8,6 +8,31 @@
 7. Click 'Create Public Gist'
 8. Add URL of your new Gist below
 
+#### How To Collect a Gpuvis Capture:
+1. Open SteamVR Settings
+2. Click 'Developer'
+3. Ensure the 'Enable GPU profiling' checkbox is checked
+4. Restart SteamVR
+5. Follow the xterm prompt to complete the gpu profiler setup
+6. Open the following URL while SteamVR is running:
+  * http://localhost:8998/dashboard/debugcommands.html
+7. Click on the 'gpu\_profiler\_capture' button
+  * Note: Try to activate the capture process while the issue is happening.
+  * The gpuvis profiler only keeps a few seconds of buffered data in memory.
+7. In gpuvis, click 'File'->'Save as'
+8. Save the file to a location you can access
+9. Upload the file to Google Drive, Dropbox or your preferred file sharing site.
+10. Paste a link to the file in the performance section below.
+
+#### How To Collect a Perf Top Snapshot:
+1. Run 'sudo perf top' from the commandline
+2. Copy the output to the clipboard when the issue occurs
+4. Browse to https://gist.github.com/
+5. Click in the text entry box (by the 1)
+6. Paste clipboard contents
+7. Click 'Create Public Gist'
+8. Paste a link to the gist in the performance section below.
+
 #### Your system information
 * Steam client version (build number or date): 
 * Distribution (e.g. Ubuntu): 
@@ -17,6 +42,11 @@
 * Opted into SteamVR beta?: [Yes/No]
 * Have you checked for system updates?: [Yes/No]
 
+#### (Optional) Performance data:
+The following fields are helpful in diagnosing performance issues:
+* Gpuvis capture:
+* Perf top gist:
+
 #### Please describe your issue in as much detail as possible:
 Describe what you _expected_ should happen and what _did_ happen. Please link any large code pastes as a [Github Gist](https://gist.github.com/)