chore: add development guide (open-telemetry#358)

Author: mayurkale22

doc/development-guide.md

@@ -0,0 +1,80 @@
+# Development Guide
+
+Before contributing to this open source project, read our [CONTRIBUTING](../CONTRIBUTING.md). We gratefully welcome improvements to documentation as well as to code.
+
+The code base is a monorepo. We use [Lerna](https://lerna.js.org/) for managing inter-module dependencies, which makes it easier to develop coordinated changes between the modules. Instead of running lerna directly, the commands are wrapped with `yarn`;
+
+### Requirements
+
+Since this project supports multiple Node versions, using a version
+manager such as [nvm](https://github.com/creationix/nvm) is recommended.
+
+We use [yarn](https://yarnpkg.com/) for its workspace functionality, so make sure to install that as well.
+
+To get started once you have Node and yarn installed, run:
+
+```sh
+$ yarn
+```
+
+This will install all the necessary modules.
+
+### Testing
+
+#### Unit Tests
+
+To run the all unit tests, use:
+
+```sh
+$ yarn test
+```
+
+To run the unit tests continuously in watch mode while developing, use:
+
+```sh
+$ yarn tdd
+```
+
+### Linting
+
+We use [gts](https://www.npmjs.com/package/gts) to make sure that new code is conform to our coding standards.
+
+Before raising a pull request, make sure there are no lint problems.
+
+To check the linter, use:
+```sh
+$ yarn run check
+```
+
+To fix the linter, use:
+```sh
+$ yarn fix
+```
+
+### Continuous Integration
+
+We rely on CircleCI 2.0 for our tests. If you want to test how the CI behaves
+locally, you can use the CircleCI Command Line Interface as described here:
+https://circleci.com/docs/2.0/local-jobs/
+
+After installing the `circleci` CLI, simply run one of the following:
+
+```sh
+$ circleci build --job lint
+$ circleci build --job node8
+$ circleci build --job node10
+$ circleci build --job node11
+$ circleci build --job node12
+$ circleci build --job node12-browsers
+```
+
+### Docs
+
+We use [typedoc](https://www.npmjs.com/package/typedoc) to generate the api documentation.
+
+To generate the docs, use:
+```sh
+$ yarn docs
+```
+
+The document will be available under `packages/opentelemetry-types/docs/out` path.