Fix missing multiplication operator in pendulum example

Add missing multiplication operator between 0.1 and sin(t) in the
pendulum external torque definition. In Julia, you cannot write
0.1sin(t) - you need 0.1 * sin(t) for the multiplication operator.

This fixes a syntax error that would cause the code example to fail
when executed.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ChrisRackauckas

docs/src/getting_started.md

@@ -379,7 +379,7 @@ end
 u₀ = [θ₀, ω₀]                       # initial state vector
 tspan = (0.0, 10.0)                  # time interval
 
-M = t -> 0.1sin(t)                    # external torque [Nm]
+M = t -> 0.1 * sin(t)                    # external torque [Nm]
 
 prob = DE.ODEProblem(pendulum!, u₀, tspan, M)
 sol = DE.solve(prob)