add instructions to avoid nesting function calls #80

Moved from UCD-SERG/lab-manual#221 (opened by d-morrison on 2026-03-17); it belongs in the coding-style chapter. (The original had 3 comments; see the link back for the discussion.)

for example if_else use case_when, recode_values, or replace_values instead of nested if_else if possible

also never nest aes() inside ggplot() calls unless absolutely necessary