chore: ignore n8n child dependencies (N8N-6)

[MaSpeng]

This pull request will add the dependencies n8n-nodes-base and n8n-workflow to the dependabot ignore list as we need to manually pin them to the same version which is requested by n8n itself.

[schroedan]

So we should check (at pull request) if the versions of these dependencies in every package.json satisfy the version of npm view n8n-nodes-base version and npm view n8n-workflow version?

[MaSpeng]

No, we don't check anything at the pull request level.

Whenever we receive a pull request from dependabot for n8n it always requires manual work.

1. we need to determine the node version that the target version of n8n is natively using (from the docker image)

• this version needs to be manifested in the devcontainer and all affected GitHub workflows
• the respective types need to be manifested in the repository dependencies (sadly they often do not match with the node version)

2. we need to determine which version of n8n-nodes-base and n8n-workflow is the target version of n8n is using

• these version needs to be manifested in the repository dependencies due to the known compatibility issues
• these versions need to be manifested in each nx project (custom node)
• a distinct commit in the structure fix(<nx project name>): <commit message> (<reference>) has to be made, to allow nx to do its work when we want to create a new release for each custom node

We surely could automate this process in the CI but I think it would be quite a large workflow and would contain some barriers to overcome, for example, the evaluation of the node version of the docker image, or even finding out which version n8n uses for n8n-base-nodes and n8n-workflow.

This PR aims to reduce the unnecessary noise about pre-release versions we cannot use anyway.