ignore and annotation description

.gitignore

@@ -3,3 +3,4 @@
 /build/
 /gradle/wrapper/gradle-wrapper.jar
 /gradle/wrapper/gradle-wrapper.properties
+/node_modules

README.md

@@ -97,3 +97,7 @@ It adds 4 bytes to the serialized data.
 ## @Unisgned
 
 This __field annontation__ allows to store __integer fields__ of any size more compact by not saving the sign. Could be applyed to both signed and unsigned integers of any size.
+
+## @FixedSize(size)
+
+Use it with fixed-size collections (like hashes, keys, etc) to not to keep collection size in the packed binary. It saves at least one byte.