Update README with improved content and formatting (#2081)

* Update README after subproject split

* Move logo path from app to core module
* Remove Tasks from synctools description
* Clean up third-party libraries section

* Update README with improved formatting and content

* Add emoji and key features section
* Improve support and contribution sections
* Clean up whitespace and formatting
* Update donation and purchase links

Author: rfc2822

README.md

@@ -1,47 +1,47 @@
-
 [![Follow @davx5app@fosstodon.org](https://img.shields.io/mastodon/follow/109598783742737223?domain=https%3A%2F%2Ffosstodon.org&style=flat-square)](https://fosstodon.org/@davx5app)
 [![Website](https://img.shields.io/website?style=flat-square&up_color=%237cb342&url=https%3A%2F%2Fwww.davx5.com)](https://www.davx5.com/)
 [![License](https://img.shields.io/github/license/bitfireAT/davx5-ose?style=flat-square)](https://github.com/bitfireAT/davx5-ose/blob/main/LICENSE)
 [![F-Droid](https://img.shields.io/f-droid/v/at.bitfire.davdroid?style=flat-square)](https://f-droid.org/packages/at.bitfire.davdroid/)
 ![GitHub Downloads (all assets, all releases)](https://img.shields.io/github/downloads/bitfireAT/davx5-ose/total?label=GitHub%20downloads)
 
-![DAVx⁵ logo](app/src/main/res/mipmap-xxxhdpi/ic_launcher.png)
-
+![DAVx⁵ logo](core/src/main/res/mipmap-xxxhdpi/ic_launcher.png)
 
-DAVx⁵
+📱 DAVx⁵
 ========
 
 > [!IMPORTANT]
 > Please see the [DAVx⁵ Web site](https://www.davx5.com) for
 > comprehensive information about DAVx⁵, including a list of services it has been tested with,
 > a manual and FAQ.
 
+✨ **Key features**
+
+* CalDAV/CardDAV synchronization for Android
+* Live [WebDAV file access over Storage Access Framework](https://manual.davx5.com/webdav_mounts.html)
+* Contacts, calendars, and tasks sync
+* Open-source and privacy-focused
+* Supports self-hosted servers
+* Easy setup with automatic configuration
+
 DAVx⁵ is licensed under the [GPLv3 License](LICENSE).
 
-News and updates: 
+📰 **News and updates**: 
 
 * [@davx5app@fosstodon.org](https://fosstodon.org/@davx5app) on Mastodon
 
-**Help, feature requests, bug reports: [DAVx⁵ discussions](https://github.com/bitfireAT/davx5-ose/discussions)**
+🗨️ **Help, feature requests, bug reports: [DAVx⁵ discussions](https://github.com/bitfireAT/davx5-ose/discussions)**
+
+## Support & Contribution
+
+* [Support guidelines](SUPPORT.md) – How to get help and report issues
+* [Contribution guidelines](CONTRIBUTING.md) – How to contribute to DAVx⁵
+* [Security policy](SECURITY.md) – Responsible vulnerability disclosure
 
 Parts of DAVx⁵ have been outsourced into these libraries:
 
 * [cert4android](https://github.com/bitfireAT/cert4android) – custom certificate management
 * [dav4jvm](https://github.com/bitfireAT/dav4jvm) – WebDAV/CalDav/CardDAV framework
-* [synctools](https://github.com/bitfireAT/synctools) – iCalendar/vCard/Tasks processing and content provider access
+* [synctools](https://github.com/bitfireAT/synctools) – iCalendar/vCard processing and content provider access
 
-**If you want to support DAVx⁵, please consider [donating to DAVx⁵](https://www.davx5.com/donate)
+💰 **If you want to support DAVx⁵, please consider [donating to DAVx⁵](https://www.davx5.com/donate)
 or [purchasing it](https://www.davx5.com/download).**
-
-
-USED THIRD-PARTY LIBRARIES
-==========================
-
-The most important libraries which are used by DAVx⁵ (alphabetically):
-
-* [dnsjava](https://github.com/dnsjava/dnsjava) – [BSD License](https://github.com/dnsjava/dnsjava/blob/master/LICENSE)
-* [ez-vcard](https://github.com/mangstadt/ez-vcard) – [New BSD License](https://github.com/mangstadt/ez-vcard/blob/master/LICENSE)
-* [iCal4j](https://github.com/ical4j/ical4j) – [New BSD License](https://github.com/ical4j/ical4j/blob/develop/LICENSE.txt)
-* [okhttp](https://square.github.io/okhttp) – [Apache License, Version 2.0](https://square.github.io/okhttp/#license)
-
-See _About / Libraries_ in the app for all used libraries and their licenses.