fix(docs): _.merge doesn't concat arrays

[agilgur5]

Summary

Small change to the docs to fix a reference to how _.merge deep merges work with arrays

Details

• it's a deep merge that merges them by index

• Per include in tsconfigDefaults is overridden by index from original tsconfig.json #226 (comment) , the rest of the docs are accurate, just this one mention was incorrect

• Per Shallow merge in tsconfigOverride where TS does so -- match tsconfig extends #86 (comment) , eventually should move to shallow merge/replace arrays to better reflect how tsconfig extends works (and principle of least surprise), but just fix the docs for now

References

Will be closing out #226 after this as it duplicates #86 otherwise

• I would've made this PR like 2 years ago to fix the docs, but unfortunately when randos on the internet are abusive to you because they only believe in their own opinion and then don't contribute anything anyway, it is not very motivational, to say the absolute least 😕 (see also my current status)