fix: Ensure title is added to default figure

[jnumainville]

Fixes #147

This was because the title was not being added to the default figure, but it should be as it is assumed to never change.

Tested with the code in the issue as well

from deephaven import empty_table, merge, time_table
from deephaven.plot import express as dx

t0 = empty_table(0).update(["x=i", "y=i*Math.random()*i", "z=i%5"])
t1 = empty_table(10).update(["x=i", "y=i*Math.random()*i", "z=i%5"])
t2 = time_table("PT1s").update(["x=i", "y=i*Math.random()*i", "z=i%5"]).drop_columns(["Timestamp"])
t3 = t2.where("x > 1")
p0 = dx.line(t0, x="x", y="y", by=["z"], title="Hello World0")
p1 = dx.line(t1, x="x", y="y", by=["z"], title="Hello World1")
p2 = dx.line(t2, x="x", y="y", by=["z"], title="Hello World2")
p3 = dx.line(t3, x="x", y="y", by=["z"], title="Hello World3")

[dsmmcken]

as it is assumed to never change.

maybe not a relevant comment, but titles can change if it was a dh.ui variable yeah?

@ui.component
def mycomponent():
  [my_title, set_title] = useState()
  i = ui.input("", onchange ... set_title)
  p=dx.line(t, title=title)

[jnumainville]

as it is assumed to never change.

maybe not a relevant comment, but titles can change if it was a dh.ui variable yeah?

@ui.component
def mycomponent():
  [my_title, set_title] = useState()
  i = ui.input("", onchange ... set_title)
  p=dx.line(t, title=title)

Yes titles can change in that case, but that creates a new chart, it doesn't modify this one.
This case was already handled by #386