Refactor Child Rendering to accept Observable

[hmallen99]

The createElement function currently accepts a list of child nodes that are immediately rendered, which makes it hard for content to be dynamic. To handle one part of this, the Ternary component was implemented, which accepted a boolean observable and returned a truthy or falsy node. This does not feel like the correct API, though, as we would need to special case switch statements, if then statements, and the null case, not to mention rendering lists of content.

To solve this issue, we should instead accept an observable as the children argument in createElement. This observable emits a stable key and a PipeNode, The latter of which gets attached to the parent element (or updates an existing element with the stable key). This allows for all of the dynamic content items to be implemented at once, rather than special casing each of them.

[github-actions]

LCOV of commit 226b733 during Continuous Integration Checks #15

Summary coverage rate:
  lines......: 100.0% (122 of 122 lines)
  functions..: 100.0% (9 of 9 functions)
  branches...: 92.6% (25 of 27 branches)

Files changed coverage rate:
                                    |Lines       |Functions  |Branches    
  Filename                          |Rate     Num|Rate    Num|Rate     Num
  ========================================================================
  packages/pipe/src/createElement.ts| 100%    102| 100%     6| 100%     22