untested. but this should work quite nicely

_docs/PKGBUILD.templates.d/release/05.package

@@ -0,0 +1,4 @@
+package() {
+        install -D -m755 ${srcdir}/${_pkgname}/src/${_pkgname} ${pkgdir}/usr/bin/${_pkgname}
+        install -D -m644 ${srcdir}/${_pkgname}/docs/README.html.en ${pkgdir}/usr/share/doc/${_pkgname}/README.html
+}