Fixes invalid escape sequences (#78)

Uses raw strings to supress the `SyntaxWarning` thrown by python3.12

Co-authored-by: Sebastian Ehlert <28669218+awvwgk@users.noreply.github.com>

Author: jevandezande

assets/ci/build-env.yaml

@@ -3,7 +3,7 @@ channels:
   - conda-forge
 dependencies:
   - meson 0.58.0
-  - fpm 0.3.0
+  - fpm
   - cmake
   - ninja
   - gcovr

python/dftd3/interface.py

@@ -199,7 +199,7 @@ def new_param(**kwargs):
 
 
 class RationalDampingParam(DampingParam):
-    """
+    r"""
     Rational damping function for DFT-D3.
     The original scheme was proposed by Becke and Johnson\ :footcite:`becke2005,johnson2005,johnson2006`
     and implemented in a slightly adjusted form using only the C8/C6 ratio in the critical
@@ -238,7 +238,7 @@ def new_param(*, s6=1.0, s8, s9=1.0, a1, a2, alp=14.0):
 
 
 class ZeroDampingParam(DampingParam):
-    """
+    r"""
     Original DFT-D3 damping function,\ :footcite:`grimme2010` based on a variant proposed by
     Chai and Head-Gordon.\ :footcite:`chai2008`
     Since it is damping the dispersion energy to zero at short distances it is usually
@@ -309,7 +309,7 @@ def new_param(*, s6=1.0, s8, s9=1.0, a1, a2, alp=14.0):
 
 
 class ModifiedZeroDampingParam(DampingParam):
-    """
+    r"""
     Modified zero damping function for DFT-D3.\ :footcite:`smith2016`
     This scheme adds an additional offset parameter to the zero damping scheme
     of the original DFT-D3.
@@ -348,7 +348,7 @@ def new_param(*, s6=1.0, s8, s9=1.0, rs6, rs8=1.0, alp=14.0, bet):
 
 
 class OptimizedPowerDampingParam(DampingParam):
-    """
+    r"""
     Optimized power version of the rational damping parameters.\ :footcite:`witte2017`
     The functional form of the damping function is modified by adding an additional
     zero-damping like power function.