improve documentation of "attention weighting" syntax

docs/features/PROMPTS.md

@@ -91,7 +91,7 @@ The InvokeAI prompting language has the following features:
 ### Attention weighting 
 Append a word or phrase with `-` or `+`, or a weight between `0` and `2` (`1`=default), to decrease or increase "attention" (= a mix of per-token CFG weighting multiplier and, for `-`, a weighted blend with the prompt without the term).
 
-The following will be recognised:
+The following syntax is recognised:
   * single words without parentheses: `a tall thin man picking apricots+`
   * single or multiple words with parentheses: `a tall thin man picking (apricots)+` `a tall thin man picking (apricots)-` `a tall thin man (picking apricots)+` `a tall thin man (picking apricots)-` 
   * more effect with more symbols `a tall thin man (picking apricots)++`
@@ -99,6 +99,40 @@ The following will be recognised:
   * all of the above with explicit numbers `a tall thin man picking (apricots)1.1` `a tall thin man (picking (apricots)1.3)1.1`. (`+` is equivalent to 1.1, `++` is pow(1.1,2), `+++` is pow(1.1,3), etc; `-` means 0.9, `--` means pow(0.9,2), etc.)
   * attention also applies to `[unconditioning]` so `a tall thin man picking apricots [(ladder)0.01]` will *very gently* nudge SD away from trying to draw the man on a ladder
 
+You can use this to increase or decrease the amount of something:
+
+`a man picking apricots from a tree`
+![an AI generated image of a man picking apricots from a tree](../assets/prompt_syntax/apricots-0.png)
+
+Using `-` to reduce apricot-ness:
+
+| `a man picking apricots- from a tree` | `a man picking apricots-- from a tree` | `a man picking apricots--- from a tree` |
+| -- | -- | -- |
+| ![an AI generated image of a man picking apricots from a tree, with smaller apricots](../assets/prompt_syntax/apricots--1.png) | ![an AI generated image of a man picking apricots from a tree, with even smaller and fewer apricots](../assets/prompt_syntax/apricots--2.png) | ![an AI generated image of a man picking apricots from a tree, with very few very small apricots](../assets/prompt_syntax/apricots--3.png) |
+
+Using `+` to increase apricot-ness:
+
+| `a man picking apricots+ from a tree` | `a man picking apricots++ from a tree` | `a man picking apricots+++ from a tree` | `a man picking apricots++++ from a tree` | `a man picking apricots+++++ from a tree` |
+| -- | -- | -- |
+| ![an AI generated image of a man picking apricots from a tree, with larger, more vibrant apricots](../assets/prompt_syntax/apricots-1.png) | ![an AI generated image of a man picking apricots from a tree with even larger, even more vibrant apricots](../assets/prompt_syntax/apricots-2.png) | ![an AI generated image of a man picking apricots from a tree, but the man has been replaced by a pile of apricots](../assets/prompt_syntax/apricots-3.png) | ![an AI generated image of a man picking apricots from a tree, but the man has been replaced by a mound of giant melting-looking apricots](../assets/prompt_syntax/apricots-4.png) | ![an AI generated image of a man picking apricots from a tree, but the man and the leaves and parts of the ground have all been replaced by giant melting-looking apricots](../assets/prompt_syntax/apricots-5.png) |
+
+You can also change the balance between different parts of a prompt:
+
+`mountain man`
+![an AI generated image of a mountain man](../assets/prompt_syntax/mountain-man.png)
+
+More mountain:
+
+| `mountain+ man` | `mountain++ man` | `mountain+++ man` | 
+| -- | -- | -- |
+| ![](../assets/prompt_syntax/mountain1-man.png) | ![](../assets/prompt_syntax/mountain2-man.png) | ![](../assets/prompt_syntax/mountain3-man.png) |
+
+More man:
+
+| `mountain man+` | `mountain man++` | `mountain man+++` | `mountain man++++` | 
+| -- | -- | -- | -- |
+| ![](../assets/prompt_syntax/mountain-man1.png) | ![](../assets/prompt_syntax/mountain-man2.png) | ![](../assets/prompt_syntax/mountain-man3.png) | ![](../assets/prompt_syntax/mountain-man4.png) |
+
 ### Blending between prompts
 
 * `("a tall thin man picking apricots", "a tall thin man picking pears").blend(1,1)`
@@ -119,7 +153,6 @@ Generate an image with a given prompt, record the seed of the image,
 and then use the `prompt2prompt` syntax to substitute words in the
 original prompt for words in a new prompt. This works for `img2img` as well.
 
-
 * `a ("fluffy cat").swap("smiling dog") eating a hotdog`.
   * quotes optional: `a (fluffy cat).swap(smiling dog) eating a hotdog`.
   * for single word substitutions parentheses are also optional: `a cat.swap(dog) eating a hotdog`.
@@ -130,6 +163,8 @@ original prompt for words in a new prompt. This works for `img2img` as well.
 * Convenience option `shape_freedom` (0-1) to specify how much "freedom" Stable Diffusion should have to change the shape of the subject being swapped. 
   * `a (cat).swap(dog, shape_freedom=0.5) eating a hotdog`.
 
+
+
 The `prompt2prompt` code is based off [bloc97's
 colab](https://github.com/bloc97/CrossAttentionControl).