Add system requirements in README

README.md

@@ -12,4 +12,8 @@
 
 The `lsm-tree` library is a Haskell implementation of [log-structured merge-trees](https://en.wikipedia.org/wiki/Log-structured_merge-tree), based on [Monkey](https://dl.acm.org/doi/abs/10.1145/3035918.3064054), that provides an on-disk key-value store.
 
-It has a number of custom features that are primarily tailored towards performant disk IO in the Haskell implementation of the Ouroboros-family of consensus algorithms, which can be found in [the `ouroboros-consensus` repository](https://github.com/IntersectMBO/ouroboros-consensus). Nevertheless, this library should be generally useful for projects that require an on-disk key-value store.
+It has a number of custom features that are primarily tailored towards performant disk IO in the Haskell implementation of the Ouroboros-family of consensus algorithms, which can be found in [the `ouroboros-consensus` repository](https://github.com/IntersectMBO/ouroboros-consensus). Nevertheless, this library should be generally useful for projects that require an on-disk key-value store.
+
+## System requirements
+
+This library only supports 64-bit, little-endian systems.