Add a benchmark with a long list of references

benchmark/samples/block-ref-list.md

@@ -0,0 +1,50 @@
+[item 1]: <1>
+[item 2]: <2>
+[item 3]: <3>
+[item 4]: <4>
+[item 5]: <5>
+[item 6]: <6>
+[item 7]: <7>
+[item 8]: <8>
+[item 9]: <9>
+[item 10]: <10>
+[item 11]: <11>
+[item 12]: <12>
+[item 13]: <13>
+[item 14]: <14>
+[item 15]: <15>
+[item 16]: <16>
+[item 17]: <17>
+[item 18]: <18>
+[item 19]: <19>
+[item 20]: <20>
+[item 21]: <21>
+[item 22]: <22>
+[item 23]: <23>
+[item 24]: <24>
+[item 25]: <25>
+[item 26]: <26>
+[item 27]: <27>
+[item 28]: <28>
+[item 29]: <29>
+[item 30]: <30>
+[item 31]: <31>
+[item 32]: <32>
+[item 33]: <33>
+[item 34]: <34>
+[item 35]: <35>
+[item 36]: <36>
+[item 37]: <37>
+[item 38]: <38>
+[item 39]: <39>
+[item 40]: <40>
+[item 41]: <41>
+[item 42]: <42>
+[item 43]: <43>
+[item 44]: <44>
+[item 45]: <45>
+[item 46]: <46>
+[item 47]: <47>
+[item 48]: <48>
+[item 49]: <49>
+[item 50]: <50>