docs(examples): Add quick start guide for gmsh example

New file: examples/gmsh_heat_equation/QUICK_START.md (34 lines)

Minimal quick-reference document:
- Links to main files (example, geometry, tutorial)
- 5-point workflow summary
- Academic usage code snippet (Issue #183)
- Matrix extraction pattern for external solvers

Complements README.md with even shorter entry point

examples/gmsh_heat_equation/QUICK_START.md

@@ -0,0 +1,34 @@
+# Gmsh Heat Equation Example
+
+Complete workflow demonstration addressing [Issue #183](https://github.com/JuliaFEM/JuliaFEM.jl/issues/183).
+
+## Quick Links
+
+- **Working Example:** `gmsh_heat_equation.jl`
+- **Gmsh Geometry:** `unit_square.geo`
+- **Comprehensive Tutorial:** `../../docs/book/gmsh_tutorial.md`
+
+## What's Here
+
+This example shows:
+1. Mesh generation with Gmsh
+2. Loading mesh into JuliaFEM  
+3. FEM assembly (K and M matrices)
+4. Extracting matrices for external solvers
+5. Integration with DifferentialEquations.jl
+
+## Academic Usage (Issue #183)
+
+If you want JuliaFEM for **discretization only** (not built-in physics):
+
+```julia
+# After assembly:
+K = problem.assembly.K  # Stiffness matrix
+M = problem.assembly.M  # Mass matrix
+f = problem.assembly.f  # Force vector
+
+# ODE system: M * du/dt = -K * u + f
+# Now use with your own solver!
+```
+
+See tutorial for complete explanation.