Add h3 function_descriptions.csv

It has been generated from the README, using duckdb, like:
COPY (SELECT function, description, '' as comment, '' as example FROM 'README.md') TO 'function_descriptions.csv';

extensions/h3/docs/function_descriptions.csv

@@ -0,0 +1,53 @@
+function,description,comment,example
+h3_latlng_to_cell,Convert latitude/longitude coordinate to cell ID,"",""
+h3_cell_to_lat,Convert cell ID to latitude,"",""
+h3_cell_to_lng,Convert cell ID to longitude,"",""
+h3_cell_to_latlng,Convert cell ID to latitude/longitude,"",""
+h3_cell_to_boundary_wkt,Convert cell ID to cell boundary,"",""
+h3_get_resolution,Get resolution number of cell ID,"",""
+h3_get_base_cell_number,Get base cell number of cell ID,"",""
+h3_string_to_h3,Convert VARCHAR cell ID to UBIGINT,"",""
+h3_h3_to_string,Convert BIGINT or UBIGINT cell ID to VARCHAR,"",""
+h3_is_valid_cell,True if this is a valid cell ID,"",""
+h3_is_res_class_iii,True if the cell's resolution is class III,"",""
+h3_is_pentagon,True if the cell is a pentagon,"",""
+h3_get_icosahedron_faces,List of icosahedron face IDs the cell is on,"",""
+h3_cell_to_parent,Get coarser cell for a cell,"",""
+h3_cell_to_children,Get finer cells for a cell,"",""
+h3_cell_to_center_child,Get the center finer cell for a cell,"",""
+h3_cell_to_child_pos,Get a sub-indexing number for a cell inside a parent,"",""
+h3_child_pos_to_cell,Convert parent and sub-indexing number to a cell ID,"",""
+h3_compact_cells,Convert a set of single-resolution cells to the minimal mixed-resolution set,"",""
+h3_uncompact_cells,Convert a mixed-resolution set to a single-resolution set of cells,"",""
+h3_grid_disk,Find cells within a grid distance,"",""
+h3_grid_disk_distances,"Find cells within a grid distance, sorted by distance","",""
+h3_grid_disk_unsafe,"Find cells within a grid distance, with no pentagon distortion","",""
+h3_grid_disk_distances_unsafe,"Find cells within a grid distance, sorted by distance, with no pentagon distortion","",""
+h3_grid_ring_unsafe,"Find cells exactly a grid distance away, with no pentagon distortion","",""
+h3_grid_path_cells,Find a grid path to connect two cells,"",""
+h3_grid_distance,Find the grid distance between two cells,"",""
+h3_cell_to_local_ij,"Convert a cell ID to a local I,J coordinate space","",""
+h3_local_ij_to_cell,"Convert a local I,J coordinate to a cell ID","",""
+h3_cell_to_vertex,Get the vertex ID for a cell ID and vertex number,"",""
+h3_cell_to_vertexes,Get all vertex IDs for a cell ID,"",""
+h3_vertex_to_lat,Convert a vertex ID to latitude,"",""
+h3_vertex_to_lng,Convert a vertex ID to longitude,"",""
+h3_vertex_to_latlng,Convert a vertex ID to latitude/longitude coordinate,"",""
+h3_is_valid_vertex,True if passed a valid vertex ID,"",""
+h3_is_valid_directed_edge,True if passed a valid directed edge ID,"",""
+h3_origin_to_directed_edges,Get all directed edge IDs for a cell ID,"",""
+h3_directed_edge_to_cells,Convert a directed edge ID to origin/destination cell IDs,"",""
+h3_get_directed_edge_origin,Convert a directed edge ID to origin cell ID,"",""
+h3_get_directed_edge_destination,Convert a directed edge ID to destination cell ID,"",""
+h3_cells_to_directed_edge,Convert an origin/destination pair to directed edge ID,"",""
+h3_are_neighbor_cells,True if the two cell IDs are directly adjacent,"",""
+h3_directed_edge_to_boundary_wkt,Convert directed edge ID to linestring WKT,"",""
+h3_get_hexagon_area_avg,Get average area of a hexagon cell at resolution,"",""
+h3_cell_area,Get the area of a cell ID,"",""
+h3_edge_length,Get the length of a directed edge ID,"",""
+h3_get_num_cells,Get the number of cells at a resolution,"",""
+h3_get_res0_cells,Get all resolution 0 cells,"",""
+h3_get_pentagons,Get all pentagons at a resolution,"",""
+h3_great_circle_distance,Compute the great circle distance between two points (haversine),"",""
+h3_cells_to_multi_polygon_wkt,Convert a set of cells to multipolygon WKT,"",""
+h3_polygon_wkt_to_cells,Convert polygon WKT to a set of cells,"",""