Fix formatting and improve clarity in isf_list.md

Author: pkawak

Manual/isf_list.md

@@ -1,7 +1,9 @@
 <h1>isf_list</h1>
 
-Calculate intermediate scattering function, using a trajectory list.
+Calculate intermediate scattering function using a trajectory list.
 
-_isf\_list \<output file\> \<list name\> \<plane\> \<first wavenumber index\> \<last wavenumber index\>_
+```
+isf_list <output file> <list name> <plane> <first wavenumber index> <last wavenumber index>
+```
 
-Options for _\<geometry\>_ are _xyz, xy, xz, yz, x, y,_ and _z_. This chooses which dimensions in k-space to include in the calculation of the intermediate scattering function. _xyz_ computes the full radial three dimensional isf, _xy, yz, and xz_ calculate two-dimensional in-plane radial isf's, and _x, y, and z_ compute one-dimensional isf's.
+Options for `<plane>` are `xyz`, `xy`, `xz`, `yz`, `x`, `y`, and `z`. This chooses which dimensions in $k$-space to include in the calculation of the intermediate scattering function. `xyz` computes the full radial three dimensional isf, `xy`, `yz`, and `xz` calculate two-dimensional in-plane radial isf's, and `x`, `y`, and `z` compute one-dimensional isf's.