Add exact arithmetic implementation and tests

- Introduced exact arithmetic with support for large integers and fractions in `exact.gd`, `big_integer.gd`, and `exact_value.gd`.
- Implemented a comprehensive test suite in `test_exact_math.gd` to validate arithmetic operations against expected results.
- Added a README in `math` directory to document the exact arithmetic system and its usage.
- Ensured that all arithmetic operations maintain precision without floating-point errors, using a custom representation for large numbers.
- Included methods for encoding and decoding exact values for serialization.

data/csv_loader.gd

@@ -0,0 +1,36 @@
+class_name CSVLoader
+
+
+static func load(csv_text: String) -> Array[Dictionary]:
+    var rows: Array[Dictionary] = []
+
+    var lines := csv_text.strip_edges().split("\n")
+
+    if lines.size() < 2:
+        return rows
+
+    var headers := lines[0].split(",")
+
+    for i in range(1, lines.size()):
+        var line := lines[i].strip_edges()
+
+        if line.is_empty():
+            continue
+
+        var values := line.split(",")
+
+        if values.size() != headers.size():
+            push_warning(
+                "CSV row %d has %d columns, expected %d"
+                % [i + 1, values.size(), headers.size()]
+            )
+            continue
+
+        var row: Dictionary = {}
+
+        for j in range(headers.size()):
+            row[headers[j].strip_edges()] = values[j].strip_edges()
+
+        rows.append(row)
+    print(rows)
+    return rows