Add support for pmtiles output format (#55)

* add pmtiles.hpp from github.com/protomaps/PMTiles [#10]

* tippecanoe main writes pmtiles output. [#10]

* detect output format using suffix
* after mbtiles is done writing, replace with pmtiles based on map/image tables.
* add method to write_json for writing json sub-object.

* tippecanoe-decode reads pmtiles input. [#10]

* tile-join reads and writes pmtiles. [#10]

* pmtiles test suite for decode and tile-join [#10]

* add base GitHub CI action for compiling and test suite.

* update pmtiles.hpp with z>15 fix

* Fix some ordering problems with pmtiles decode

* Pmtiles should also pass the raw tiles tests

* Eradicate spaces from tileset metadata JSON fields

* Eradicate spaces from more test fixtures

* Update more tests

* Pmtiles tests pass now too

* Remove unnecessary sort (and make indent)

* Update changelog

* The allow-existing test for pmtiles needs -o, not -e

* Declare --allow-existing to be unsupported for pmtiles.

It was always a bad idea even for mbtiles.

Co-authored-by: Brandon Liu <bdon@bdon.org>

tile.cpp

@@ -1998,7 +1998,7 @@ long long write_tile(FILE *geoms, std::atomic<long long> *geompos_in, char *meta
 			prefilter_jp = json_begin_file(prefilter_read_fp);
 		}
 
-		for (size_t seq = 0; ; seq++) {
+		for (size_t seq = 0;; seq++) {
 			serial_feature sf;
 			ssize_t which_partial = -1;
 
@@ -3040,7 +3040,7 @@ int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpo
 		size_t zoom_tile_size = 0;
 		size_t zoom_feature_count = 0;
 
-		for (size_t pass = 0; ; pass++) {
+		for (size_t pass = 0;; pass++) {
 			pthread_t pthreads[threads];
 			std::vector<write_tile_args> args;
 			args.resize(threads);