Allow specifying flavour in `.mega-linter.yml`

[MRDGH2821]

Is your feature request related to a problem? Please describe.
I frequently use mega linter locally, it would be nice if in config file itself I specify which flavour I want to use.

Describe the solution you'd like
A config like:

USE_FLAVOUR: javascript

Describe alternatives you've considered
I can use VSCode's tasks.json, which works when I use npm/node installed in system. It falls apart if I use fnm.
Also tasks.json is likely not portable across code editors.

Additional context
Another setting can be put to ignore this config option when mega-linter is running in ci.

[echoix]

If indeed there's no other way now, it seems like a legit config to have

[nvuillam]

As this is the docker image that reads the yaml configuration, it's not possible to do the contrary :/

What we could eventually do is update mega-linter-runner so it reads .mega-linter.yml file , and if there is MEGALINTER_RUNNER_FLAVOR , use from its internal call to docker run

Would you like to submit a Pull Request implementing such feature ?