Add Link to Paper for Weakly Enforced BCs to Docs (#1811)

* Add Paper for Weakly Enforced BCs to Docs

* spelling

docs/literate/src/files/non_periodic_boundaries.jl

@@ -16,6 +16,8 @@
 # state as arguments, and solves an approximate Riemann problem to introduce dissipation (and
 # hence stabilization) at the boundary. Hence, the performance of the Dirichlet BC depends on the
 # fidelity of the numerical surface flux.
+# An easy-to read introductory reference on this topic is the paper by 
+# [Mengaldo et al.](https://doi.org/10.2514/6.2014-2923).
 
 # The passed boundary value function is called with the same arguments as an initial condition
 # function, i.e.