Add more snippet types for better detection

docs/reference/images/pixel.md

@@ -6,7 +6,7 @@ Get the state of a pixel in an [Image](/reference/images/image).
 
 ### JavaScript
 
-```
+```sig
 export function pixel(_this: micro_bit.Image, x: number, y: number) : boolean
 ```
 
@@ -29,7 +29,7 @@ This example gets the state of pixel `0, 0` in the `img` variable:
 
 ### ~hide
 
-```
+```blocks
 let img = images.createImage(`
 . . # . . . . . . .
 . # . # . . . # . .
@@ -41,7 +41,7 @@ let img = images.createImage(`
 
 ### ~
 
-```
+```blocks
 let state = img.pixel(0, 0)
 ```
 

docs/reference/images/show-frame.md

@@ -6,7 +6,7 @@ Display an [Image](/reference/images/image) on the BBC micro:bit's [LED screen](
 
 ### JavaScript
 
-```
+```sig
 export function showFrame(img: micro_bit.Image, frame: number)
 ```
 
@@ -20,7 +20,7 @@ The `show frame` function is the same as [plot frame](/reference/images/plot-fra
 
 ### Example
 
-```
+```blocks
 let img = images.createImage(`
 # . . . # # . . . #
 . # . # . . # # # .

docs/reference/images/width.md

@@ -20,7 +20,7 @@ The following example gets the width of `img` and stores it in the `w` variable:
 
 ### ~hide
 
-```
+```blocks
 let img = images.createImage(`
 . . # . . . . . . .
 . # . # . . . # . .
@@ -32,7 +32,7 @@ let img = images.createImage(`
 
 ### ~
 
-```
+```blocks
 let w = img.width()
 ```
 
@@ -40,7 +40,7 @@ let w = img.width()
 
 The following example uses the `width` function with a [for](/blocks/loops/for) loop to show each image frame on the screen:
 
-```
+```blocks
 let img2 = images.createImage(`
 . . # . . . # # # # . # # # .
 . # # . . . . . . # . . . # .