chore(native): add example of global fingerprint setting (#14524)

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### Link to updated example [vercel
preview](https://sentry-docs-git-joshua-nativefingerprinting.sentry.dev/platforms/native/usage/sdk-fingerprinting/#basic-example)

## DESCRIBE YOUR PR
This came up in a Discord thread, and we didn't really have this
documented anywhere.

For manual event captures, we already provide a simple
`sentry_value_set_by_key(event, "fingerprint", fp);` example, but this
does not help with fingerprinting crashes. Hence I added an example of
using `sentry_set_fingerprint("myFingerPrint", NULL);` which sets the
global fingerprint list to `["myFingerPrint"]`.

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## SLA

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Thanks in advance for your help!

## PRE-MERGE CHECKLIST

*Make sure you've checked the following before merging your changes:*

- [x] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter
experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs
team](https://github.com/orgs/getsentry/teams/docs)

---------

Co-authored-by: Karl Heinz Struggl <[email protected]>

Author: JoshuaMoelans

platform-includes/set-fingerprint/basic/native.mdx

@@ -1,3 +1,15 @@
+You can set a fingerprint to be added to **all future events and errors**:
+```c
+#include <sentry.h>
+
+sentry_set_fingerprint("myFingerPrint", NULL); // overwrites existing fingerprints
+my_fingerprinted_function(); // events are grouped on "myFingerPrint"
+
+sentry_clear_fingerprint(); // clears all fingerprints
+```
+
+For specific, manually captured events, fingerprints can be added to the `fingerprint` key of the event. This will be prioritized over the globally set fingerprint:
+
 ```cpp
 #include <sentry.h>