fix: add Readme

README.md

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+# cdk-notifier
+lightweight CLI tool to parse a CDK log file and post changes to pull request requests.
+Can be used to get more confidence on approving pull requests because reviewer will be aware of changes done to your environments.
+
+## Install
+
+Install binary with latest release
+```bash
+curl -L "https://github.com/karlderkaefer/cdk-notifier/releases/latest/download/cdk-notifier_$(uname)_amd64.gz" -o cdk-notifier.gz
+gunzip cdk-notifier.gz && chmod +x cdk-notifier && rm -rf cdk-notifier.gz
+sudo mv cdk-notifier /usr/local/bin/cdk-notifier
+```
+Check Version and help
+```bash
+cdk-notifier --version
+# 1.0.1
+
+cdk-notifier --help
+#Post CDK diff log to Github Pull Request
+#
+#Usage:
+#  cdk-notifier [flags]
+#
+#Flags:
+#  -d, --delete                delete comments when no changes are detected for a specific tag id (default true)
+#  -o, --github-owner string   Name of gitub owner. If not set will lookup for env var $CIRCLE_PROJECT_USERNAME
+#  -r, --github-repo string    Name of github repository without organisation. If not set will lookup for env var $CIRCLE_PROJECT_REPONAME
+#      --github-token string   Github token used to post comments to PR
+#  -h, --help                  help for cdk-notifier
+#  -l, --log-file string       path to cdk log file (default "./data/cdk-small.log")
+#  -p, --pull-request-id int   Id of github pull request. If not set will lookup for env var $CIRCLE_PR_NUMBER (default 23)
+#  -t, --tag-id string         unique identifier for stack within pipeline (default "stack")
+#  -v, --verbosity string      Log level (debug, info, warn, error, fatal, panic) (default "info")
+#      --version               version for cdk-notifier
+```
+
+## Usage
+First create the output of cdk diff to file. You can stream cdk diff to stdout and to file with following.
+This tool most like runs in a CI environment. To avoid [printing millions of lines](https://github.com/aws/aws-cdk/issues/8893#issuecomment-654296389) you add progress flag.
+```bash
+cdk diff --progress=events &> >(tee cdk.log)
+```
+cdk-notifier will then analyze and transform the log by
+* remove ASCII colors
+* prepare additions and deletion for GitHub markdown diff
+* truncate log if exceeding [max length of body for comment](https://git.luolix.topmunity/t/maximum-length-for-the-comment-body-in-issues-and-pr/148867/2)
+and then send
+
+cdk-notifier will post the processed log of cdk diff to PR if there are changes.
+If a diff comment for tag-id exists and no changes are detected then comment will delete. 
+You can control this behavior with `--delete false`.
+
+```bash
+cdk-notfier --github-owner some-org --githhub-repo some-repo --github-token 1234 --log-file ./cdk.log --tag-id my-stack
+```
+The `tag-id` has to be unique within one pipeline. It's been used to identify the comment to update or delete.
+
+## Running on CirlceCI
+If you run cdk-notifier on CircleCi you dont need to set owner, repo or token. 
+CircleCi will provide default variables which will read in by cdk-notifier when cli arg is not set.
+```bash
+CIRCLE_PR_NUMBER
+CIRCLE_PROJECT_REPONAME
+```
+but you need the add environment variable for github token or set CLi arg `github-token`.
+```bash
+GITHUB_TOKEN
+```
+
+## Versioning
+Use [Conventional Commit Messages](https://www.conventionalcommits.org/en/v1.0.0/).
+[Semantic Release](https://github.com/semantic-release/semantic-release) will release a new version with changelog.
+
+examples:
+``` 
+# increase patch version
+fix: fixing tests
+
+# incease minor version
+feat: add configuration
+
+# increase major version:
+feat: remove comments api
+
+BREAKING CHANGE: remove comments api
+
+# update docu
+docs: update readme
+```
+
+