Make lazy nested signals work

Feature Request

Currently lazy nested signal do not work $foo.bar.bam = 3 will result in an error if the foo and bar objects do not already exist.

Datastar Version

No response

[jasalt]

Echoing from a support request I sent that this affects initializing nested values using data-on-load the following way:

Example (Codepen):

<span>nested:</span>
<div data-on-load="$dataload.mode = 'intial mode'"
     data-signals-datasignals.mode="'initial mode'">
  <span>data-on-load</span>
  <h1 data-text="$dataload.mode"></h1>
  <span>data-signals</span>
  <h1 data-text="$datasignals.mode"></h1> 
</div>

<span>non-nested:</span>
<div data-on-load="$dataloadmode = 'intial mode'"
     data-signals-sigmode="'initial mode'">
  <span>data-on-load</span>
  <h1 data-text="$dataloadmode"></h1>
  <span>data-signals</span>
  <h1 data-text="$sigmode"></h1> 
</div>

Output:

One workaround is to use data-signals instead as shown in the example.

[wilaak]

I'm also experiencing issues in regards to data-effect handlers not properly updating on nested signal changes.