Update constants.py to follow PEP 8 naming convention

src/pymatlib/data/constants.py

 from dataclasses import dataclass
 
-
 @dataclass
 class Constants:
     """
     A dataclass to store fundamental constants.
-
     Attributes:
-        temperature_room (float): Room temperature in Kelvin.
-        N_a (float): Avogadro's number, the number of constituent particles (usually atoms or molecules) in one mole of a given substance.
-        amu (float): Atomic mass unit in kilograms.
-        e (float): Elementary charge, the electric charge carried by a single proton or the magnitude of the electric charge carried by a single electron.
-        speed_of_light (float): Speed of light in vacuum in meters per second.
+        TEMPERATURE_ROOM (float): Room temperature in Kelvin.
+        N_A (float): Avogadro's number, the number of constituent particles (usually atoms or molecules) in one mole of a given substance.
+        AMU (float): Atomic mass unit in kilograms.
+        E (float): Elementary charge, the electric charge carried by a single proton or the magnitude of the electric charge carried by a single electron.
+        SPEED_OF_LIGHT (float): Speed of light in vacuum in meters per second.
     """
-    temperature_room: float = 298.15  # Room temperature in Kelvin
-    N_a: float = 6.022141e23  # Avogadro's number, /mol
-    amu: float = 1.660538e-27  # Atomic mass unit, kg
-    e: float = 1.60217657e-19  # Elementary charge, C
-    speed_of_light: float = 0.299792458e9  # Speed of light, m/s
+    TEMPERATURE_ROOM: float = 298.15  # Room temperature in Kelvin
+    N_A: float = 6.022141e23  # Avogadro's number, /mol
+    AMU: float = 1.660538e-27  # Atomic mass unit, kg
+    E: float = 1.60217657e-19  # Elementary charge, C
+    SPEED_OF_LIGHT: float = 0.299792458e9  # Speed of light, m/s