fix: cancelling task doesn't finish child's spawned processes

[cristianoliveira]

When the child task also spawns a process, the child.kill() wasn't enough to fully cancel it. By using the unix signal we ensure it will be clean closed before starting the task again.

For instance, jest spawns multiple workers and Funzzy wasn't closing all of them. After this change, it cancels the current jest run properly

user:op-integrator-dashboard/ (feat/pagination-for-merchant-listing) $ ps aux | grep jest                                                                                                                                                       [9:16:01]
user  5046  49.7  0.2 34850360  35308 s035  S+    9:16AM   0:00.22 /usr/local/Cellar/node/20.2.0/bin/node /Users/user/work/op-integrator-dashboard/node_modules/jest-worker/build/workers/processChild.js
user  5047  49.5  0.2 34850360  35504 s035  R+    9:16AM   0:00.22 /usr/local/Cellar/node/20.2.0/bin/node /Users/user/work/op-integrator-dashboard/node_modules/jest-worker/build/workers/processChild.js
user  5049  49.1  0.2 34850360  35284 s035  S+    9:16AM   0:00.22 /usr/local/Cellar/node/20.2.0/bin/node /Users/user/work/op-integrator-dashboard/node_modules/jest-worker/build/workers/processChild.js
user  5045  47.8  0.2 34850360  36104 s035  S+    9:16AM   0:00.23 /usr/local/Cellar/node/20.2.0/bin/node /Users/user/work/op-integrator-dashboard/node_modules/jest-worker/build/workers/processChild.js
user  5048  47.0  0.2 34850360  35188 s035  R+    9:16AM   0:00.22 /usr/local/Cellar/node/20.2.0/bin/node /Users/user/work/op-integrator-dashboard/node_modules/jest-worker/build/workers/processChild.js
user  5051  46.4  0.2 34850360  35740 s035  R+    9:16AM   0:00.22 /usr/local/Cellar/node/20.2.0/bin/node /Users/user/work/op-integrator-dashboard/node_modules/jest-worker/build/workers/processChild.js
user  5050  46.0  0.2 34850360  35340 s035  R+    9:16AM   0:00.22 /usr/local/Cellar/node/20.2.0/bin/node /Users/user/work/op-integrator-dashboard/node_modules/jest-worker/build/workers/processChild.js
user  5008  32.7  0.9 56050952 152792 s035  S+    9:16AM   0:01.26 node /Users/user/work/op-integrator-dashboard/node_modules/.bin/jest --watch --no-watch
user  5075   0.0  0.0 34121332    660 s010  S+    9:16AM   0:00.00 grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --exclude-dir=.idea --exclude-dir=.tox jest