Added Rocket case study example to Optimal Control folder

[PetiteChouette]

Description of example:
The rocket problem is an Optimal Control problem dealing with optimizing final time of a rocket's position from 0 to 10 units of distance away, in this case. Mass, velocity and force over time are also shown graphically.

Reason for addition:
Expansion of the library of optimal control examples, this one solving for final time specifically.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.77%. Comparing base (724d56f) to head (07a9dfd).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #431   +/-   ##
=======================================
  Coverage   99.77%   99.77%           
=======================================
  Files          39       39           
  Lines        6791     6791           
=======================================
  Hits         6776     6776           
  Misses         15       15           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[pulsipher]

Thanks for this. It looks good, just needs a little more information up front.

[pulsipher]

This needs to be formatted more like an optimization problem. See

InfiniteOpt.jl/docs/src/examples/Optimal Control/hovercraft.jl

Lines 8 to 17 in 724d56f

	# The corresponding dynamic optimization problem is expressed:
	# ```math
	# \begin{aligned}
	# &&\underset{x(t), v(t), u(t)}{\text{min}} &&& \int_{t \in T} |u(t)|_2^2 dt \\
	# &&\text{s.t.} &&& v(0) = v0\\
	# &&&&& \frac{dx}{dt} = v(t), && t \in T\\
	# &&&&& \frac{dv}{dt} = u(t), && t \in T\\
	# &&&&& x(t_i) = xw_i, && i \in I
	# \end{aligned}
	# ```

for an example. We also need to define what all the variables are and describe the the overall goal of the problem in a little more detail.