feat: documentation site (#1101)

## Description

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## Related Issue

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## Changes Made

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- Change 1
- Change 2
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## Testing Performed

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## Checklist

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- [ ] I have tested these changes locally and they work as expected.
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- [ ] I have updated the documentation to reflect these changes, if
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Documentation**
- Enhanced project README for clarity and improved environment variables
section.
- Added comprehensive developer and user documentation, including guides
on local development, public API, self-hosting, and compliance
standards.
- Introduced specific guides for contributing, creating API keys, using
webhooks, and setting up security measures.
- Detailed documentation on various fields available for document
signing to improve user understanding.
- Added metadata structuring to improve navigation within the
documentation site.

- **Chores**
  - Updated `.gitignore` to better handle project files.

- **New Features**
- Introduced detailed metadata and documentation for various Documenso
functionalities, including signing documents, user profiles, and
compliance levels.
- Added functionality for Direct Link Signing, enabling easy sharing for
document signing.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Timur Ercan <timur.ercan31@gmail.com>
Co-authored-by: Lucas Smith <me@lucasjamessmith.me>
Co-authored-by: David Nguyen <davidngu28@gmail.com>

apps/documentation/package.json

@@ -0,0 +1,35 @@
+{
+  "name": "@documenso/documentation",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev -p 3002",
+    "build": "next build",
+    "start": "next start -p 3002",
+    "lint:fix": "next lint --fix",
+    "clean": "rimraf .next && rimraf node_modules",
+    "copy:pdfjs": "node ../../scripts/copy-pdfjs.cjs"
+  },
+  "dependencies": {
+    "@documenso/assets": "*",
+    "@documenso/lib": "*",
+    "@documenso/tailwind-config": "*",
+    "@documenso/trpc": "*",
+    "@documenso/ui": "*",
+    "next": "14.0.3",
+    "next-plausible": "^3.12.0",
+    "nextra": "^2.13.4",
+    "nextra-theme-docs": "^2.13.4",
+    "react": "^18",
+    "react-dom": "^18"
+  },
+  "devDependencies": {
+    "@types/node": "^20",
+    "@types/react": "^18",
+    "@types/react-dom": "^18",
+    "autoprefixer": "^10.0.1",
+    "postcss": "^8",
+    "tailwindcss": "^3.3.0",
+    "typescript": "^5"
+  }
+}