Add example to README

README.md

@@ -7,4 +7,29 @@
 [![codecov](https://codecov.io/github/Seelengrab/FieldFlags.jl/branch/main/graph/badge.svg?token=PBH8NJCHKS)](https://codecov.io/github/Seelengrab/FieldFlags.jl)
 
 FieldFlags.jl is a small package for declaring [bitfield](https://en.wikipedia.org/wiki/Bit_field)-like structs, without
-having to manually mask out bits. For more information, check out the [documentation](https://seelengrab.github.io/FieldFlags.jl/)!
+having to manually mask out bits. For more information, check out the [documentation](https://seelengrab.github.io/FieldFlags.jl/)!
+
+```julia-repl
+julia> using FieldFlags
+
+julia> @bitfield mutable struct Foo
+           a:1
+           b:2
+           _:7
+           c:3
+       end
+
+# The type only takes up 2 bytes
+julia> sizeof(Foo)
+2
+
+julia> f = Foo(1,2,3)
+Foo(a: true, b: 0x2, c: 0x3)
+
+julia> f.a = 2
+2
+
+# Assignments truncate leading bits!
+julia> f.a
+false
+```