Update build pipeline

[programming-wolf]

Pipeline builds now, but we do have several content issues now.

• Pipes and Filters cannot be found (but should be there)
• term-tools-and-material-approach.adoc is apparently included but it does not even exist (any more)
• several warnings about missing language tags.

[gernotstarke]

I'm not sure I understand everything, but as the build process does not directly affect content, I like to merge anyway.

[gernotstarke]

• tools-and-materials is NOT included (which is ok, as it is no longer relevant)
• pipes and filters are included, and appear in the generated versions DE and EN