vscode settings and contributing (#50)

.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "rewrap.wrappingColumn": 80,
+    "editor.rulers": [80, 120],
+    "markdownlint.config": {
+        "MD013": true
+    },
+}

CONTRIBUTING.md

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+# Contributing
+
+Welcome to OpenTelemetry specifications repository!
+
+Before you start - see OpenTelemetry general
+[contributing](https://github.com/open-telemetry/community/blob/master/CONTRIBUTING.md)
+requirements and recommendations.
+
+## Proposing a change
+
+TODO: describe the RFC process https://github.com/open-telemetry/community/issues/56
+
+## Writing specs
+
+Specification is written in markdown format. Please make sure files are rendered
+OK on GitHub.
+
+We highly encourage to use line breaks in markdown files at `80` characters
+wide. There are tools that can do it for you effectively. Please submit proposal
+to include your editor settings required to enable this behavior so the out of
+the box settings for this repository will be consistent.