Add LLVM statepoints document

Author: jacob-hughes

softdev.bib

@@ -3396,3 +3396,12 @@ @misc{rustlangref
     month = Sep,
     author = {The Rust Developers},
 }
+
+@misc{llvm14statepoints,
+    title = {Garbage collection with {LLVM}},
+    author = {The {LLVM} Project},
+    year = {2014},
+    month = Dec,
+    howpublished = {\url{https://llvm.org/docs/GarbageCollection.html}},
+    note = {Accessed: 2023-04-03},
+}