Clarify that int and decimal bigInt, bigDecimal (#2608)

fix [#2396](https://github.com/microsoft/typespec/issues/2396)

common/changes/@typespec/compiler/big-int-decimal-doc_2023-10-26-21-09.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@typespec/compiler",
+      "comment": "",
+      "type": "none"
+    }
+  ],
+  "packageName": "@typespec/compiler"
+}

docs/standard-library/built-in-data-types.md

@@ -186,7 +186,8 @@ scalar bytes
 
 ### `decimal` {#decimal}
 
-A decimal number with any length and precision.
+A decimal number with any length and precision. This represent any `decimal` value possible.
+It is commonly represented as `BigDecimal` in some languages.
 
 ```typespec
 scalar decimal
@@ -286,7 +287,8 @@ scalar int8
 
 ### `integer` {#integer}
 
-A whole number
+A whole number. This represent any `integer` value possible.
+It is commonly represented as `BigInteger` in some languages.
 
 ```typespec
 scalar integer

packages/compiler/lib/lib.tsp

@@ -11,7 +11,8 @@ scalar bytes;
 scalar numeric;
 
 /**
- * A whole number
+ * A whole number. This represent any `integer` value possible.
+ * It is commonly represented as `BigInteger` in some languages.
  */
 scalar integer extends numeric;
 
@@ -76,7 +77,8 @@ scalar float64 extends float;
 scalar float32 extends float64;
 
 /**
- * A decimal number with any length and precision.
+ * A decimal number with any length and precision. This represent any `decimal` value possible.
+ * It is commonly represented as `BigDecimal` in some languages.
  */
 scalar decimal extends numeric;