Add benchmark. Looks slow :/

Bench.cpp

@@ -0,0 +1,27 @@
+#include "Facade.h"
+
+#include <nanobench.h>
+
+void monotonicallyIncreasing() {
+  constexpr int kWindow = 100;
+  ankerl::nanobench::Bench bench;
+  Facade facade{0};
+  bench.warmup(kWindow).run("monotonically increasing", [&] {
+    const int64_t remove = __builtin_bswap64(facade.getVersion() - kWindow);
+    const int64_t next = __builtin_bswap64(facade.getVersion());
+    weaselab::VersionedMap::Mutation mutations[] = {
+        {(const uint8_t *)&remove, nullptr, 8, 0,
+         weaselab::VersionedMap::Clear},
+        {(const uint8_t *)&next, (const uint8_t *)&next, 8, 8,
+         weaselab::VersionedMap::Set},
+    };
+    facade.addMutations(mutations, sizeof(mutations) / sizeof(mutations[0]),
+                        facade.getVersion() + 1);
+    facade.viewAt(std::max<int64_t>(0, facade.getVersion() - kWindow / 2))
+        .rangeRead({}, {0xff}, 0, false);
+    facade.setOldestVersion(
+        std::max<int64_t>(0, facade.getVersion() - kWindow));
+  });
+}
+
+int main() { monotonicallyIncreasing(); }