Adds DEVELOPMENT.md

.gitignore

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 /tmp/
 **.idea/
 *.DS_Store
+**/process.yml

DEVELOPMENT.md

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+# Development Guide
+
+## Running CircleCI locally
+
+### Step 1: Install CircleCI
+
+If you wish to run CircleCI locally, start by installing it:
+
+- macOS
+```
+brew install circleci
+```
+
+- Linux (via Snap)
+```
+sudo snap install docker circleci
+sudo snap connect circleci:docker docker
+```
+
+- Windows (via Chocolatey)
+```
+choco install circleci-cli -y
+```
+
+### Step 2: Run CircleCI
+
+To run a job, export the config to `process.yml`, and specify it when executing:
+```shell
+circleci config process .circleci/config.yml > process.yml
+circleci local execute -c process.yml --job JOB_NAME
+```