Added boundary (#13)

* Made materials seperation for the elements

* Refactor HeatConduction2DFin.html layout and enhance gmshQuadReader.js for improved file handling; update plotSolutionScript.js for responsive plotting

* Refactor importGmshQuadTri function to improve readability and structure; remove deprecated importGmsh function

* Add mesh file for rectangular triangular domain with defined physical names and nodes

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Co-authored-by: Sridhar.Mani <sridhar.mani@novacastindia.com>

Author: sridhar-mani