Add README

Author: DarcyRaynerDD

README.md

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+# datadog-lambda-extension
+[![CircleCI](https://circleci.com/gh/DataDog/datadog-agent/tree/master.svg?style=svg&circle-token=dbcee3f02b9c3fe5f142bfc5ecb735fdec34b643)](https://circleci.com/gh/DataDog/datadog-agent/tree/master)
+[![Slack](https://chat.datadoghq.com/badge.svg?bg=632CA6)](https://chat.datadoghq.com/)
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+
+AWS Lambda Extension that supports submitting custom metrics, traces and logs synchronously while your AWS Lambda function executes. 
+
+## Installation
+
+Follow the [installation instructions](https://docs.datadoghq.com/serverless/datadog_lambda_library/extension/), and view your function's enhanced metrics, traces and logs in Datadog.
+
+## Environment Variables
+
+### DD_API_KEY
+
+The Datadog API Key must be defined by setting one of the following environment variables:
+
+- DD_API_KEY - the Datadog API Key in plain-text, NOT recommended
+- DD_KMS_API_KEY - the KMS-encrypted API Key, requires the `kms:Decrypt` permission
+
+### DD_SITE
+
+Possible values are `datadoghq.com`, `datadoghq.eu`, `us3.datadoghq.com` and `ddog-gov.com`. The default is `datadoghq.com`.
+
+### DD_LOG_LEVEL
+
+Set to `debug` enable debug logs from the Datadog Lambda Extension. Defaults to `info`.
+
+## Configuration file
+
+Using a configuration file is supported (note that environment variable settings
+override the value from the configuration file): you only have to create a [`datadog.yaml`](https://docs.datadoghq.com/agent/guide/agent-configuration-files/?tab=agentv6v7)
+file in the root of your lambda function.
+
+### Logs filtering and scrubbing support
+
+The Datadog Lambda Extension supports using the different logs filtering / scrubbing features of the Datadog Agent. All you have to do is to set `processing_rules` in the `logs_config`
+field of your configuration.
+
+Please refer to the public documentation for all filtering and scrubbing features:
+
+* https://docs.datadoghq.com/agent/logs/advanced_log_collection/?tab=configurationfile#global-processing-rules
+* https://docs.datadoghq.com/agent/logs/advanced_log_collection/?tab=configurationfile#filter-logs
+
+## Opening Issues
+
+If you encounter a bug with this package, we want to hear about it. Before opening a new issue, search the existing issues to avoid duplicates.
+
+When opening an issue, include the Datadog Lambda Layer version, and stack trace if available. In addition, include the steps to reproduce when appropriate.
+
+You can also open an issue for a feature request.
+
+
+## Contributing
+
+If you find an issue with this package and have a fix, please feel free to open a pull request following the [procedures](https://github.com/DataDog/datadog-agent/blob/master/docs/dev/contributing.md).
+
+## Community
+
+For product feedback and questions, join the `#serverless` channel in the [Datadog community on Slack](https://chat.datadoghq.com/).
+
+## License
+
+Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+
+This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2021 Datadog, Inc.