Added alias targets to Engine and Interop

[capnkenny]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Updates the Engine and Interop targets to be callable via aliases (NovelRT::Engine and NovelRT::Interop) when referenced by projects via FetchContent

Is there an open issue that this resolves? If so, please link it here.
No

What is the current behavior? (You can also link to an open issue here)
When a user pulls NovelRT down via FetchContent, they are required to link to the Engine target directly instead of being able to use the NovelRT::Engine target (akin to using an "installed" / find_package version of NovelRT).

What is the new behavior (if this is a feature change)?
Users using FetchContent can now use the aliases OR the direct target names.

Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
Nope

[github-actions]

Test Results

       4 files  ±0         4 suites  ±0   1m 16s ⏱️ -25s
   693 tests ±0     693 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
2 772 runs  ±0  2 772 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit d9d12d8. ± Comparison against base commit 97c1823.

[RubyNova]

LGTM