docs: add role description

docs/docs/usage/_category_.json

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+{
+  "label": "Usage",
+  "position": 3
+}

docs/docs/usage/roles.md

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+---
+sidebar_position: 1
+---
+
+# Roles
+
+There are two types of roles in LandTCMS: "Global roles" and "Project roles".
+
+## Global roles
+
+This role is tied to each user's information and affects the entire site, regardless of the project.
+There are two types of roles:
+
+- Administrator
+- User
+
+Administrators can manage site-wide settings and users from the “Administration” menu.
+
+## Project roles
+
+This role can be set for members participating in each project.
+There are three types of roles:
+
+- Manager
+- Developer
+- Reporter
+
+### Permissions for each role
+
+#### Project
+
+| Action | Manager/Owner | Developer | Reporter | Not member |
+| ------ | ------------- | --------- | -------- | ---------- |
+| Delete | ✅            | ❌        | ❌       | ❌         |
+| Update | ✅            | ❌        | ❌       | ❌         |
+| Read   | ✅            | ✅        | ✅       | 🌓         |
+
+#### Project Members
+
+| Action      | Manager/Owner | Developer | Reporter | Not member |
+| ----------- | ------------- | --------- | -------- | ---------- |
+| Add         | ✅            | ❌        | ❌       | ❌         |
+| Delete      | ✅            | ❌        | ❌       | ❌         |
+| Change role | ✅            | ❌        | ❌       | ❌         |
+| Read        | ✅            | ✅        | ✅       | 🌓         |
+
+#### Folders and Test cases
+
+| Action | Manager/Owner | Developer | Reporter | Not member |
+| ------ | ------------- | --------- | -------- | ---------- |
+| Create | ✅            | ✅        | ❌       | ❌         |
+| Delete | ✅            | ✅        | ❌       | ❌         |
+| Update | ✅            | ✅        | ❌       | ❌         |
+| Read   | ✅            | ✅        | ✅       | 🌓         |
+
+#### Test runs
+
+| Action | Manager/Owner | Developer | Reporter | Not member |
+| ------ | ------------- | --------- | -------- | ---------- |
+| Create | ✅            | ✅        | ✅       | ❌         |
+| Delete | ✅            | ✅        | ✅       | ❌         |
+| Update | ✅            | ✅        | ✅       | ❌         |
+| Read   | ✅            | ✅        | ✅       | 🌓         |
+
+1. "Owner" and "Not member" are not role. "Owner" is the user who created project.
+   "Not member" means a user who is not a project member
+1. 🌓 means that read permission is only allowed if the project is set to public.