docs: Ensure all headers are parsed by Doxygen (#681)

Because we had moved some headers outside of src/nanoarrow into
src/nanoarrow/common, they weren't getting included in the
documentation!

We can't quite add `-W` to the sphinx build command (error for warnings)
because pandoc doesn't generate .rst files that are warning free (and we
use pandoc to avoid having to write tutorials in restructured text).

Closes #676.

python/src/nanoarrow/array.py

@@ -116,7 +116,7 @@ class Array(ArrayViewVisitable):
     the Arrow C Stream interface.
 
     Note that an :class:`Array` is not necessarily contiguous in memory (i.e.,
-    it may consist of zero or more ``ArrowArray``s).
+    it may consist of zero or more ``ArrowArray`` objects).
 
     Parameters
     ----------

src/apidoc/Doxyfile

@@ -187,7 +187,7 @@ FILE_PATTERNS          = *.c \
                          *.ucf \
                          *.qsf \
                          *.ice
-RECURSIVE              = NO
+RECURSIVE              = YES
 EXCLUDE                =
 EXCLUDE_SYMLINKS       = NO
 EXCLUDE_PATTERNS       =