Add alternative element-local mapping (to be merged before #31)

[tristanmontoya]

This PR adds the element-local mapping from Guba et al. (2014), which first maps the quadrature node coordinates from the reference element using a bilinear mapping based on the four corner vertices, and then projects the mapped nodes onto a sphere of radius $a$ by scaling the resulting Cartesian coordinates $\boldsymbol{x}$ by $a/\lVert\boldsymbol{x} \rVert_2$. This is a quadrilateral version of what Michael Baldauf does for triangular grids (e.g. in this paper).

[codecov]

Codecov Report

Attention: Patch coverage is 96.42857% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.31%. Comparing base (15062dc) to head (d3bc8f7).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...olvers/dgsem_p4est/containers_2d_manifold_in_3d.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
+ Coverage   81.78%   82.31%   +0.53%     
==========================================
  Files           8        8              
  Lines         829      854      +25     
==========================================
+ Hits          678      703      +25     
  Misses        151      151              

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