Pipelines installed through the /pipelines/add should all install the "requirements" in frontmatter spec

[zabirauf]

Currently I see that the only place where pipelines dependencies are installed is when pipelines docker is started through PIPELINES_URLS. But when the API pipelines/add is called from OpenWebUI those dependencies are not installed. Both for consistency and easy of used to add new pipelines in OpenWebUI the requirements frontmatter should be respected through the API calls as well.

[xuchenCN]

LGTM +1

[zabirauf]

Create PR #192 to fix this