docs: update readme (#22)

.env.example

@@ -1,5 +1,10 @@
+# Generate a personal access token (classic) on GitHub with an account that has read access to the repository
+# cf. https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/creating-a-personal-access-token
 GITHUB_ACCESS_TOKEN=
 
+# Generate a Personal API Tokens on CircleCI with an account linked to the GitHub repository
+# cf. https://circleci.com/docs/managing-api-tokens
 CIRCLECI_ACCESS_TOKEN=
 
+# Specify the absolute path of the filename to output the list of event times. If not specified, the current directory is set.
 OUTPUT_DIR=

README.md

@@ -1 +1,54 @@
 # depwatch
+
+depwatch is a simple command-line tool for collecting the times of various events in your project's lifecycle, from code commits to deployments. Event times are retrieved from repository management tools (like GitHub) and CI tools (like CircleCI).
+
+## Installation
+
+Install depwatch using pip:
+
+```shell-session
+$ pip install depwatch
+```
+
+## Usage
+
+Execute the command with your access tokens.
+
+```shell-session
+GITHUB_ACCESS_TOKEN=<your_token> CIRCLECI_ACCESS_TOKEN=<your_token> depwatch <user_name>/<repository_name>
+```
+
+The results are output to the output.csv file.
+
+```shell-session
+$ cat output.csv
+first_committed_at,merged_at,deployed_at
+2023-02-25T00:48:18+00:00,2023-02-25T00:57:06+00:00,2023-02-25T00:58:11+00:00
+2023-02-25T00:46:52+00:00,2023-02-25T00:54:05+00:00,2023-02-25T00:55:12+00:00
+2023-02-25T00:43:47+00:00,2023-02-25T00:45:33+00:00,2023-02-25T00:46:39+00:00
+...
+```
+
+### Note: Using the `.env` file
+
+Alternatively, you can use the `.env` file. Create the `.env` file in the directory where you want to run the command as follows.
+
+```shell-session
+cp .env.example .env
+```
+
+Set the values according to the instructions in the `.env` file.
+
+### Note: Scope of the GitHub Personal Access Token
+
+GitHub offers [two types of personal access tokens](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/creating-a-personal-access-token), fine-grained personal access tokens and classic personal access tokens. For personal repositories, you can use both. For organizatio repositories, we recommend using classic tokens, as we know that fine-grained tokens do not allow you to get private repositories.
+
+If you use fine-grained personal access tokens, specify read-only permissions for **Contents**, **Metadata**, and **Pull requests**. If you use classic personal access tokens, specify **repo** scope.
+
+## Contributing
+
+Comming soon!
+
+## License
+
+This code is released under the MIT License. See [LICENSE](/LICENSE) for details.