docs: update readme (#1091)

* updated readme

* added link to C+20 requirement issue

* Add build prerequisites into readme

* Added additional link to Contributing.md

* apply suggestion from code review

Co-authored-by: Mischan Toosarani-Hausberger <mischan@abovevacant.com>

* apply suggestions from code review

---------

Co-authored-by: Mischan Toosarani-Hausberger <mischan@abovevacant.com>

Author: JoshuaMoelans

README.md

@@ -42,21 +42,20 @@ Using the `sentry-native` SDK in a standalone use case is currently an experimen
 ## Downloads
 
 The SDK can be downloaded from the [Releases] page, which also lists the
-changelog of every version.
+changelog of every version. We recommend using our release packages, but if you want to use this repo directly, please follow the [contribution guide](./CONTRIBUTING.md) to understand the setup better.
 
 [releases]: https://github.com/getsentry/sentry-native/releases
 
 ### What is Inside
 
 The SDK bundle contains the following folders:
 
-- `external`: These are external projects which are consumed via
-  `git submodules`.
 - `include`: Contains the Sentry header file. Set the include path to this
   directory or copy the header file to your source tree so that it is available
   during the build.
 - `src`: Sources of the Sentry SDK required for building.
 - `ndk`: Sources for the Android NDK JNI layer.
+- `external`: These are vendored dependencies fetched via git submodules (use `git submodules update --init --recursive` if you use a git clone rather than a release).
 
 ## Platform and Feature Support
 
@@ -93,7 +92,9 @@ per platform, and can also be configured for cross-compilation.
 System-wide installation of the resulting sentry library is also possible via
 CMake.
 
-Building the Crashpad Backend requires a `C++14` compatible compiler.
+The prerequisites for building differ depending on the platform and backend. You will always need `CMake` to build the code. Additionally, when using the `crashpad` backend, `zlib` is required. On Linux and macOS, `libcurl` is a prerequisite. For more details, check out  the [contribution guide](./CONTRIBUTING.md).
+
+Building the Crashpad Backend [requires a `C++20` compatible compiler](https://github.com/getsentry/sentry-native/issues/1041). In particular, the standard library must support `std::ranges` for `mini_chromium` (a core library of `crashpad`).
 
 **Build example**: