Pkgconfig-module.md: fix typos [skip ci]
Pkgconfig-module.md: fix typos [skip ci]

Almost every keyword documented here takes this form:

  - `foo` bar

with no comma after the keyword. Make `filebase` consistent, and fix a
comma splice.

Fix 'Arbitraty' typo in `libraries` documentation.

pexip/meson,becm/meson,becm/meson,QuLogic/meson,MathieuDuponchelle/meson,pexip/meson,mesonbuild/meson,QuLogic/meson,jpakkane/meson,MathieuDuponchelle/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,jpakkane/meson,pexip/meson,becm/meson,mesonbuild/meson,MathieuDuponchelle/meson,jpakkane/meson,mesonbuild/meson,becm/meson,becm/meson,QuLogic/meson,MathieuDuponchelle/meson,pexip/meson,mesonbuild/meson,MathieuDuponchelle/meson,QuLogic/meson,becm/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,becm/meson,jpakkane/meson,jpakkane/meson,becm/meson,jpakkane/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,MathieuDuponchelle/meson,jpakkane/meson,becm/meson,becm/meson,QuLogic/meson,MathieuDuponchelle/meson,pexip/meson,pexip/meson,MathieuDuponchelle/meson,mesonbuild/meson,MathieuDuponchelle/meson,jpakkane/meson,jpakkane/meson,QuLogic/meson,QuLogic/meson,pexip/meson,pexip/meson