Update examples

examples/error.sp

@@ -1,5 +1,5 @@
 const { exit } from @'core/os';
 
-let @main in {
+let @main : i32 in {
     exit(1);
 }

examples/file.sp

@@ -1,7 +1,7 @@
 const io from @'core/io';
 const { open } from @'core/fs';
 
-let @main in {
+let @main : i32 in {
     io.out('What is your name? ');
     let name = io.in();
     let file = open('name.txt');

examples/float128.sp

@@ -2,7 +2,7 @@ const io from @'core/io';
 const { concat } from @'core/string';
 const { toString } from @'core/float_utils';
 
-let @main in {
+let @main : i32 in {
     let float1 : f128 = 234.6;
     f128 float2 : f128 = 2934748348291930404.5;
     io.outln(concat('Result is: ',toString(float1 + float2)));

examples/hello-world.sp

@@ -1,5 +1,5 @@
 const io from @'core/io';
 
-let @main in {
+let @main : i32 in {
     io.outln('Hello world!');
 }

examples/input.sp

@@ -1,6 +1,6 @@
 const io from @'core/io';
 
-let @main in {
+let @main : i32 in {
     io.out('What\'s your name? ');
     let name = io.in();
     io.out('Hello, ');

examples/new-syntax.sp

@@ -2,7 +2,7 @@ const { io } from @'core/io';
 
 const good_food : String = 'watermelon';
 
-let @main in {
+let @main : i32 in {
 
     io.outln('Hello world!');
 

examples/variables.sp

@@ -1,6 +1,6 @@
 const io from @'core/io';
 
-let @main in {
+let @main : i32 in {
     let age : i32 = 64;
     io.out('I am ');
     io.out(age);