Sets the tabs to use for this, overriding the default tabs.
`PangoLayout` will place content at the next tab position whenever it meets a Tab character (U+0009).
By default, tabs are every 8 spaces. If tabs is null, the default tabs are reinstated.
tabs is copied into the layout; you must free your copy of tabs yourself.
Note that tabs and justification conflict with each other: Justification will move content away from its tab-aligned positions. The same is true for alignments other than pango_align_left.
| this |
a `PangoLayout` |
| tabs |
a `PangoTabArray` |