Fix "forward" in cheatsheet (#1525)

This is how `"backward"` looks:

<img width="540" alt="image"
src="https://github.com/cursorless-dev/cursorless/assets/755842/e196de38-a3db-445c-af29-61758317e39e">

But `"forward"` didn't have the same special treatment:

<img width="550" alt="image"
src="https://github.com/cursorless-dev/cursorless/assets/755842/00a87f25-c806-4984-a25f-f9f9c3855e25">

This PR makes it look as follows:

<img width="546" alt="image"
src="https://github.com/cursorless-dev/cursorless/assets/755842/80bfee7f-cf4b-437d-b980-10eb68434796">

I also updated the cheatsheet json that we use to generate the [generic
cheatsheet](https://www.cursorless.org/cheatsheet) while I was here

## Checklist

- [ ] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [x] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [x] I have not broken the cheatsheet

Author: pokey

src/cheatsheet/sections/modifiers.py

@@ -26,6 +26,7 @@ def get_modifiers():
         "previous",
         "next",
         "backward",
+        "forward",
     ]
     simple_modifiers = {
         key: value
@@ -125,6 +126,10 @@ def get_modifiers():
                     "spokenForm": f"<scope> {complex_modifiers['backward']}",
                     "description": "single instance of <scope> including target, going backwards",
                 },
+                {
+                    "spokenForm": f"<scope> {complex_modifiers['forward']}",
+                    "description": "single instance of <scope> including target, going forwards",
+                },
                 {
                     "spokenForm": f"<number> <scope>s {complex_modifiers['backward']}",
                     "description": "<number> instances of <scope> including target, going backwards",