Merge branch 'web-mathjax3' into 'master'

web/content/docs/benchmarks/creepbgra/CreepBRGa.md

web/content/docs/benchmarks/elliptic/drainage_diffusion.md

...rks/elliptic/elliptic-dirichlet-volumetric-source-term.md

web/content/docs/benchmarks/elliptic/elliptic-dirichlet.md

web/content/docs/benchmarks/elliptic/elliptic-neumann.md

...ptic/elliptic-pde-with-dirichlet-and-nodal-source-term.md

web/content/docs/benchmarks/elliptic/elliptic-robin.md

web/content/docs/benchmarks/elliptic/poisson_equation.md

...ntent/docs/benchmarks/liquid-flow/drainage_Liquid_Flow.md

.../docs/benchmarks/liquid-flow/liquid-flow-theis-problem.md

...dent-heterogeneous-source-term-and-boundary-conditions.md

web/content/docs/benchmarks/phase-field/phasefield.md

web/content/docs/benchmarks/reactive-transport/calcite.md

...ent/docs/benchmarks/reactive-transport/wetland/Wetland.md

...s/thermo-hydro-mechanics/consolidation_pointheatsource.md

web/content/docs/devguide/documentation/introduction.md

...ontent/docs/tools/getting-started/video-tutorial/index.md

web/layouts/partials/header.html