docs(example): updated and fixed requires in examples

example/basics/factorial.bzi

@@ -1,5 +1,5 @@
 interface Factorial {
-  fn factorial(self: Factorial, n: int)
+  fn factorial(self: actor Factorial, n: int)
 }
 
 require "std:io"

example/basics/loop.bzi

@@ -3,7 +3,7 @@ require "std:math"
 require "std:io"
 
 interface Loopable {
-  fn loop(self: Loopable, i: int)
+  fn loop(self: actor Loopable, i: int)
 }
 
 fn Loop(msg: string) => actor < Loopable {

example/servers/http.bzi

@@ -1,7 +1,5 @@
 require "std:http": HTTPServer, send_buffer
-require "std:io"
-require "std:datatypes/string"
-require "std:math"
+require "std:foundation"
 
 let port = 8000
 let server = spawn HTTPServer(port)
@@ -10,5 +8,4 @@ server->listen(fn(req) => {
   req.send_buffer("Hello, world!")
 })
 
-
 print("Server running on port $port")