feat: Wrap error returned from run with context error

[goodevilgenius]

Fixes #1212

Previous PR: #1215

This change depends on features added in go 1.20, therefore the minimum version is bumped to that.;

This allows the error returned by p.Run to be checked for a context error.

For example, given this code:

ctx := context.WithTimeout(context.Background, time.Second*5)
p := tea.NewProgram(model, tea.WithContext(ctx))
_, err := p.Run()
if errors.Is(err, context.DeadlineExceeded) {
  // Handle timeout
}

This change now allows this to work.

This opens up more possibilities, allowing a program to cancel a context, and look for the reason for the cancellation.

Using context.Cause to get the error further allows for even more precise handling, when a context is built with context.WithCancelCause, for example:

ctx, cancel := context.WithCancelCause(context.Background())
ctx = context.WithTimeout(ctx, time.Second*5)
badThing := errors.New("a bad thing happened")

p := tea.NewProgram(model, tea.WithContext(ctx))
go func() {
  // do some stuff
  if badThingHappened {
    cancel(badThing)
  }
)()

_, err := p.Run()
switch {
case errors.Is(err, context.DeadlineExceeded):
  // Handle timeout
case errors.Is(err, badThing):
  // Handle bad thing
case err != nil:
  // Handle other errors
}