Use American English spelling of "gray"

Basic search/replace inside "core" folder.

Add "grey" to flagWords in .cspell.json

+++ b/core/modules/shortcut/shortcut.module
@@ -28,7 +28,7 @@ function shortcut_help($route_name, RouteMatchInterface $route_match) {
-      $output .= '<dd>' . t('The Shortcut module creates an add/remove link for each page on your site; the link lets you add or remove the current page from the currently-enabled set of shortcuts (if your theme displays it and you have permission to edit your shortcut set). The core Seven administration theme displays this link next to the page title, as a grey or yellow star. If you click on the grey star, you will add that page to your preferred set of shortcuts. If the page is already part of your shortcut set, the link will be a yellow star, and will allow you to remove the current page from your shortcut set.') . '</dd>';
+      $output .= '<dd>' . t('The Shortcut module creates an add/remove link for each page on your site; the link lets you add or remove the current page from the currently-enabled set of shortcuts (if your theme displays it and you have permission to edit your shortcut set). The core Seven administration theme displays this link next to the page title, as a gray or yellow star. If you click on the gray star, you will add that page to your preferred set of shortcuts. If the page is already part of your shortcut set, the link will be a yellow star, and will allow you to remove the current page from your shortcut set.') . '</dd>';

The one instance of grey in an actual string that is not related to CSS, is this hunk from the Shortcuts module, which is long to read and compare but the part in question talks about the "grey star" versus the "yellow star".

There is specific reference to the core Seven administration theme there, but in the Claro theme the disabled star is hollow/outlined and in that sense only slightly gray. So, I don't know if it makes sense to basically rewrite this string entirely to phase out the mention of Seven, but if so, that should be a follow-up issue with no real impact here.

Mentioned impact of UI string in issue summary.

The search/replace in #2 was case sensitive so I missed the capitalized instances of Greyskull. After fixing that in the patch here, I've also done a case insensitive search to ensure there weren't any others I missed.

Before patch in #7:

$ git fetch --all --prune
$ git checkout 9.1.x
$ git log --graph --oneline
* 932b36e4de (HEAD -> 9.1.x, origin/9.1.x)
$ cd core
$ find . -path "*/node_modules/*" -o -path "*/assets/vendor*" -o -type f -print0 | xargs -0 grep -I -i -o -n gray | wc -l
     164

jameswilson@Makak ~/App/Drupal/drupal-9.x-dev/core (9.1.x=) 
$ find . -path "*/node_modules/*" -o -path "*/assets/vendor*" -o -type f -print0 | xargs -0 grep -I -i -o -n grey | wc -l
     104

After patch:

$ find . -path "*/node_modules/*" -o -path "*/assets/vendor*" -o -type f -print0 | xargs -0 grep -I -i -o -n grey | wc -l
       1

$ find . -path "*/node_modules/*" -o -path "*/assets/vendor*" -o -type f -print0 | xargs -0 grep -I -i -o -n grey
./.cspell.json:37:      "grey",

$ find . -path "*/node_modules/*" -o -path "*/assets/vendor*" -o -type f -print0 | xargs -0 grep -I -i -o -n gray | wc -l
     268

Thanks @alexpott

1. I edited my comment #8 to fix the grep command to use -o option because the items found were not adding up correctly because there were several multiple instances found within a single line of code-- now they do.
2. Re #9 point 1: Fixed in current patch. Thank you for catching this. You're amazing.
   

   $ sort misc/cspell/dictionary.txt > misc/cspell/dictionary.sorted.txt 
   $ diff misc/cspell/dictionary.txt misc/cspell/dictionary.sorted.txt 
   --- misc/cspell/dictionary.txt	2020-06-27 08:18:56.000000000 -0500
   +++ misc/cspell/dictionary.sorted.txt	2020-06-27 08:20:19.000000000 -0500
   @@ -753,8 +753,8 @@
    grandgrandchild's
    granularities
    grayblue
   -greeking
    grayskull
   +greeking
    gripsmall
    groupable
    groupby
   

3. Re #9 point 2: I brought up the standardization question on #3154539: Implement new Gray scale on Claro where I first noticed this issue, and am proposing to remove the named colors for the neutral gray scale and switch to a decimal based color name variables. I would assume a naming correction would be okay too at this point, but will be sure to note that as an API change in the issue summary. Thanks for the ping to @lauriii.
4. While running yarn run spellcheck:core to sanity check things here, I found two words that are being flagged as unknown. I assume needs a follow-up issue, but I've asked about this on #2972224-170: Add .cspell.json to automate spellchecking in Drupal core (apologies for crosspost).

NR for patch and for feedback from @lauriii to address comment #9 point 2 (see also #10 point 3).

Thanks @lauriii.

AFAIK this issue is ready to go in. I've fixed the one change requested by @alexpott from #9 in my patch on #10 but my understanding is that I cannot RTBC my own work, in this case would that help this show up on core maintainers radars more quickly?