fix(template): remove TS warning while scaffolding TS templates

[deadcoder0904]

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• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
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Summarize your changes:

By default, TS gives a warning,

Missing return type on function.eslint@typescript-eslint/explicit-function-return-type

So I removed the warning by adding a return type void :)

[codecov]

Codecov Report

Merging #1664 into master will decrease coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1664      +/-   ##
==========================================
- Coverage   72.71%   72.62%   -0.10%     
==========================================
  Files          74       74              
  Lines        2210     2210              
  Branches      416      416              
==========================================
- Hits         1607     1605       -2     
- Misses        443      445       +2     
  Partials      160      160              

Impacted Files	Coverage Δ
packages/maker/flatpak/src/MakerFlatpak.ts	78.26% <0.00%> (-8.70%)	⬇️

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