Add info about limits

README.md

@@ -46,6 +46,28 @@ pub fn main() {
 
 Further documentation can be found at <https://hexdocs.pm/bigi>.
 
+## Limitations
+
+Erlang does have [a limit for big integers at around 4 megabits](https://elixirforum.com/t/is-there-an-integer-size-limit/65647/8?u=nicd),
+as demonstrated below:
+
+```gleam
+import bigi
+
+pub fn main() {
+  // Works
+  bigi.power(bigi.from_int(2), bigi.from_int(4_194_239))
+
+  // Blows up
+  bigi.power(bigi.from_int(2), bigi.from_int(4_194_240))
+}
+```
+
+For Node.js, the limit is somewhere higher.
+
+`bigi` has no facilities to warn about or handle errors due to these system limits. It is up to the developer
+to be mindful of them.
+
 ## Development
 
 ```sh