[orx-composition] Add details to README.md files (#332)

orx-composition/README.md

@@ -2,4 +2,16 @@
 
 Shape composition library
 
-This code was previously part of `openrndr-draw`.
+One can think of a Composition as a vector design made out of primitives
+like ShapeContour, Shape, or LineSegment, each having its fill color,
+stroke color and stroke weight.
+
+Compositions can be loaded from SVG files and then queried or altered via code.
+
+Composition can also be generated from scratch, typically using `drawComposition { ... }`, then saved as an SVG file.
+
+Read about Composition [in the guide](https://guide.openrndr.org/drawing/drawingSVG.html).
+
+_The code in `orx-composition` was previously found under `openrndr-draw` in the `openrndr` repository._
+
+<!-- __demos__ -->

orx-svg/README.md

@@ -2,4 +2,22 @@
 
 SVG reader and writer library.
 
-This code was previously found in `openrndr-svg`.
+## Methods
+
+```kotlin
+fun loadSVG(fileOrUrlOrSvg: String): Composition
+fun loadSVG(file: File): Composition
+
+fun parseSVG(svgString: String): Composition
+
+fun Shape.toSvg(): String
+fun ShapeContour.toSvg(): String
+
+fun Composition.saveToFile(file: File)
+fun Composition.toSVG(): String
+```
+
+Find basic examples of loading and saving SVG files 
+[in the guide](https://guide.openrndr.org/drawing/drawingSVG.html).
+
+_The code in `orx-svg` was previously found under `openrndr-svg` in the `openrndr` repository._

orx-text-writer/README.md

@@ -2,5 +2,7 @@
 
 Writing texts with layouts
 
-Code in `orx-text-writer` was previously part of `openrndr-draw`.
+The `TextWriter` class was previously called `Writer`.
+Find usage examples [in the guide](https://guide.openrndr.org/drawing/text.html#advanced-text-rendering).
 
+_The code in `orx-text-writer` was previously found under `openrndr-draw` in the `openrndr` repository._