Move backend documentation out of readme

Since I'm still not sure whether I want this or not, it's best to
keep it out of README.md

At least it allows for finding inconsistencies the existing backend

Backends.md

@@ -0,0 +1,33 @@
+## Parsing backends
+
+egui_commonmark offers __experimental__ support for using [comrak](https://crates.io/crates/comrak)
+as parsing backend. By default pulldown_cmark is used. To use comrak instead do:
+
+```toml
+egui_commonmark = { version = "0.11", default-features = false, features = ["load-images", "comrak"] }
+```
+
+### Why two parsing backends?
+
+egui_commonmark was originally implemented using pulldown_cmark, however comrak
+has stricter commonmark/github style markdown support. In addition it allows the
+crate to support more features than pulldown_cmark can offer with regards to github
+style markdown.
+
+pulldown_cmark has fewer dependencies and should theoretically be faster.
+
+Due to these reasons both backends are supported. At least for now.
+
+
+### Differences in support
+
+Currently both support the same feature set
+
+### Known rendering differences
+
+| Type    | pulldown_cmark | comrak |
+|---------|----------------|--------|
+| Footers | Placed when they appear | Placed at the end |
+| Spec incompatibilies | Blocks such as images can be rendered inside tables. This is against the spec | Disallowed |
+
+

README.md

@@ -38,39 +38,6 @@ CommonMarkViewer::new("viewer").show(ui, &mut cache, markdown);
 * `svg`: Support for viewing svg images
 * `fetch`: Images with urls will be downloaded and displayed
 
-## Parsing backends
-
-egui_commonmark offers __experimental__ support for using [comrak](https://crates.io/crates/comrak)
-as parsing backend. By default pulldown_cmark is used. To use comrak instead do:
-
-```toml
-egui_commonmark = { version = "0.11", default-features = false, features = ["load-images", "comrak"] }
-```
-
-### Why two parsing backends?
-
-egui_commonmark was originally implemented using pulldown_cmark, however comrak
-has stricter commonmark/github style markdown support. In addition it allows the
-crate to support more features than pulldown_cmark can offer with regards to github
-style markdown.
-
-pulldown_cmark has fewer dependencies and should theoretically be faster.
-
-Due to these reasons both backends are supported. At least for now.
-
-
-### Differences in support
-
-Currently both support the same feature set
-
-### Known rendering differences
-
-| Type    | pulldown_cmark | comrak |
-|---------|----------------|--------|
-| Footers | Placed when they appear | Placed at the end |
-| Spec incompatibilies | Blocks such as images can be rendered inside tables. This is against the spec | Disallowed |
-
-
 
 ## License