chore: fix mustache type warning and add some tests

[ST-DDT]

Ref: #541

[codecov]

Codecov Report

Merging #753 (0652fd5) into main (9e03bcf) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 0652fd5 differs from pull request most recent head ff485c3. Consider uploading reports for the commit ff485c3 to get more accurate results

@@           Coverage Diff           @@
##             main     #753   +/-   ##
=======================================
  Coverage   99.34%   99.34%           
=======================================
  Files        1918     1922    +4     
  Lines      176482   176476    -6     
  Branches      910      912    +2     
=======================================
  Hits       175324   175324           
+ Misses       1102     1096    -6     
  Partials       56       56           

Impacted Files	Coverage Δ
src/helpers.ts	99.28% <100.00%> (+0.13%)	⬆️
src/random.ts	99.46% <0.00%> (-0.01%)	⬇️
src/datatype.ts	100.00% <0.00%> (ø)
src/definitions/address.ts	100.00% <0.00%> (ø)
src/locales/ar/address/index.ts	100.00% <0.00%> (ø)
src/locales/en/address/index.ts	100.00% <0.00%> (ø)
src/locales/he/address/index.ts	100.00% <0.00%> (ø)
src/locales/ur/address/index.ts	100.00% <0.00%> (ø)
src/locales/ar/address/postcode_by_state.ts	100.00% <0.00%> (ø)
src/locales/en/address/postcode_by_state.ts	100.00% <0.00%> (ø)
... and 5 more