add docs to weight function

Author: aadimator

src/NetMSA.jl

@@ -182,13 +182,13 @@ end
 Return the weight of the row, calculated as:
 
 ```math
-w(r) =  \begin{equation*}
+$w(r) =  \begin{equation*}
 \begin{cases}
   w_1  \times  \frac{x}{c}; & \text{ if r is not aligned}   \\
   w_2  \times  \frac{n_s}{c}; & \text{ if r is aligned}   \\
   w_3; & \text{ if r is full}   \\
 \end{cases}
-\end{equation*}
+\end{equation*}$
 ```
 where n_s is the number of occurrences of the symbol s in the aligned row r,
 and c is the total number of columns in the row. The value of x is equal to zero
@@ -219,7 +219,7 @@ function weight(row; w1=0.25, w2=0.5, w3=1.0)
   if full(row)
     return w3;
   end
-    
+
   c = length(row);
   max = mostfrequent(row)[1];