infra: ignore .pnpm-store

[Shinigami92]

When using corepack and having a local .pnpm-store/ folder, prettier wants to format the content
This prevents prettier from doing that

[ST-DDT]

Why would the pnpm store folder be inside the project?

[codecov]

Codecov Report

Merging #2253 (6f45369) into next (0708eb4) will decrease coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #2253      +/-   ##
==========================================
- Coverage   99.60%   99.59%   -0.01%     
==========================================
  Files        2643     2643              
  Lines      245862   245862              
  Branches     1159     1156       -3     
==========================================
- Hits       244883   244875       -8     
- Misses        952      960       +8     
  Partials       27       27              

see 2 files with indirect coverage changes

[Shinigami92]

Why would the pnpm store folder be inside the project?

Because of executing statements like this: pnpm config set store-dir .pnpm-store
Source: https://pnpm.io/continuous-integration#gitlab-ci