Look for *.spec.ts files in src folder for jest tests

[FredrikJT]

• Fixes: https://github.com/tobiipro/merlin-controller-electron/issues/206
• Breaking change: [ ]

---

This PR makes it possible to run jest test files named *.spec.ts which are located in the test and src folder. The command to use this is e.g. make a.spec.ts which will find all files called a.spec.ts in the test and src folder and run them with jest.

Explanation:

• src folder added to search path
• group of names with \( \) this is optional but was part of an answer I found. It gives the command a bit more structure
• -o means or, so either *.test.js or *.spec.ts