Update README

README.md

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 # kubectl-cls
+
+List CronJobs and CronWorkflows that are scheduled and executed during a specific time period.
+
+## Installation
+
+### Homebrew
+
+TBD
+
+### Go
+
+```
+go install github.com/unblee/kubectl-cls@latest
+```
+
+### Binaries
+
+TBD
+
+## Usage
+
+The `--from` and `--to` options must be specified. Its format is RFC3339.
+
+```
+kubectl cls --from 2023-01-24T00:00:00+09:00 --to 2023-01-24T06:00:00+09:00
+Namespace     Name   Schedule             Suspend   Kind
+namespace-a   foo    */10 * * * *         false     CronJob
+namespace-b   bar    0 15 * * *           false     CronJob
+namespace-c   baz    0,15,30,45 * * * *   false     CronJob
+namespace-z   qux    */30 * * * *         false     CronWorkflow
+namespace-z   quux   0 * * * *            false     CronWorkflow
+```
+
+## Note
+
+The Kubernetes cluster is assumed to be running in UTC.