For performance reasons, Doom CLI runs in a minimal environment wherein
no `ob-<language>` libraries are initially loaded; but tangling a
document with noweb-enabled blocks can trigger an org-babel evaluation
of any noweb-addressable block; and any such evaluation will fail
tangling with an error unless the correct `ob-<language>` library has
been loaded.
So. This changes the tangle CLI function to note any noweb-addressable
labels (i.e. any `#+NAME:` or `:noweb-ref` associated with a block) when
iterating through the source document's blocks; for each block where one
is found, it conditionally attempts to `require` the corresponding
`ob-<src-lang>` library.
