more obvious absorption differences among mixtures

[#60262004]
stop slider handle keydown event from bubbling

[#47309921 #60262004]

This fixes an issue where controlling the slider handle
with the keyboard would cause the model to step backwards
and forwards in time.
Fix bug in md2d removeLine()
ITSI: Heat and Temperature 4 interactive
better energy level distribution among mixtures

[#60262004]
ITSI: Heat and Temperature 2 interactive

[#61767464]
ITSI: Heat and Temperature 2a interactive

[#61767568]
expose model.addShape/addLine to scripting api
rutherford interactive tracing tails on atoms

[#57165738]
ITSI: Fix colors in "most ammonia molecules" interactive

[#61767866]
ITSI: Add ratio selection to Getting Rations Right interactive

[#61767958]
ITSI: Fix up Choosing a Reaction interactive

[#61768118]
add getNumberOfShapes to scripting api

[#57165738]
rutherford interactive better tracing and scaling

[#57165738]
Update jsdom version (package.json)
Try to fix tests (it solves one issue, but new tests are failing now)
ITSI: Fix up Concentration and Breathing

Change bar graph colors.
Reposition elements for updated aspect ratio.

[#61169124]
ITSI: Update Dissociation Energy interactive for aspect ratio

[#61169732]
ITSI: Update Dissociation Energy interactive for aspect ratio

[#61169982]
ITSI: Fix Getting Ratios Right interactive

Change pulldown to radio buttons.
Fix aspect ratio.
Enlarge model area.
[#61767958]