Add freeze() method

[xpepermint]

No description provided.

[codecov-io]

Codecov Report

Merging #41 into master will increase coverage by 0.12%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master      #41      +/-   ##
==========================================
+ Coverage   86.02%   86.14%   +0.12%     
==========================================
  Files          62       62              
  Lines        1116     1133      +17     
  Branches      248      251       +3     
==========================================
+ Hits          960      976      +16     
  Misses         75       75              
- Partials       81       82       +1

Impacted Files	Coverage Δ
packages/rawmodel-core/src/core/props.ts	84.9% <100%> (+0.4%)	⬆️
packages/rawmodel-core/src/core/models.ts	85.65% <75%> (+0.32%)	⬆️