* Fix doc: add clarification for projection; closes#4817
Adds clarification in the documentation that specifies that the
`project` and `unproject` methods cannot take in arrays, but only
actual instances of `L.LatLng` and `L.Point`, respectively.
* Fix doc: add clarification for transform methods
Changes the word "real" for the word "actual" so that people don't
confuse actual instances of `L.Point` with coordinates using real
numbers.
* Clean up docs/examples - one directory per tutorial, more templating.
* Fix some URLs
* tutorials: update rendered CDN links to 1.0.0 and L.circle signature (#4975)
* Update shown CDN links to 1.0.0
As initially done in PR #4967, but just for the rendered links (what the users sees), as actual link / script tags are already updated.
* DOCS update L.circle to new syntax
in quick-start tutorial, following PR #4974.
* DOCS update L.circle to new syntak (example src)
updated L.circle to new signature (radius as an option instead of 2nd parameter).
* tutorials: use L.geoJSON new syntax (#4983)
* tutorials: use new syntax L.geoJSON
for consistency with recommended factory new syntax (`L.geoJSON` instead of legacy `L.geoJson`).
As done in PR #4933 for docstrings.
* tutorials: L.geoJSON new syntax in script
* Renamed several files to directory/index.md
Corrected docstrings of L.GeoJSON for methods (addData, resetStyle, setStyle) to be really counted as "methods" instead of static "functions" (geometryToLayer, coordsToLatLng, coordsToLatLngs, latLngToCoords, latLngsToCoords, asFeature)
Following https://stackoverflow.com/questions/39776919/how-to-reference-the-data-of-an-existing-geojson-leaflet-object/39787583#39787583, sounds like the current definition "decide whether to show a feature or not" implies that the data is retained in memory, but just not shown.
Replaced "show" by "include" to try to make it clearer that the filtered out data is _lost_ (not retained at all within the group).
Also took the opportunity to add a note about changing the `filter` option dynamically (no re-evaluation of child layers, whether they meet the new filter conditions or not).
