Fix a typo so it actually works, and add a test and documentation

man/tippecanoe.1

@@ -208,6 +208,23 @@ If you have a feature like this:
 with a \fB\fCtippecanoe\fR object specifiying a \fB\fCmaxzoom\fR of 9 and a \fB\fCminzoom\fR of 4, the feature
 will only appear in the vector tiles for zoom levels 4 through 9. Note that the \fB\fCtippecanoe\fR
 object belongs to the Feature, not to its \fB\fCproperties\fR\&.
+.PP
+You can also specify a layer name in the \fB\fCtippecanoe\fR object, which will take precedence over
+the filename or name specified using \fB\fC\-\-layer\fR, like this:
+.PP
+.RS
+.nf
+{
+    "type" : "Feature",
+    "tippecanoe" : { "layer" : "streets" },
+    "properties" : { "FULLNAME" : "N Vasco Rd" },
+    "geometry" : {
+        "type" : "LineString",
+        "coordinates" : [ [ \-121.733350, 37.767671 ], [ \-121.733600, 37.767483 ], [ \-121.733131, 37.766952 ] ]
+    }
+}
+.fi
+.RE
 .SH Point styling
 .PP
 To provide a consistent density gradient as you zoom, the Mapbox Studio style needs to be