feat(layout): add OPY (@robi-wan) (#6453)

### Description

Add OPY layout

https://github.com/voidyourwarranty2/opy-layout
> OPY is a keyboard layout in the tradition of NEO2, AdNW and KOY
> for a split ortholinear keyboard with shift and space on thumb keys,
> optimized for mixed English and German usage [..]

I tweaked the rows so that it looks good in the matrix and split matrix
keyboard styles. The author did not define a row1 so I took the freedom
to include one which resembles row1 from the qwertz layout.

### Checks

- [ ] Adding quotes?
- [ ] Make sure to include translations for the quotes in the
description (or another comment) so we can verify their content.
- [ ] Adding a language or a theme?
- [ ] If is a language, did you edit `_list.json`, `_groups.json` and
add `languages.json`?
  - [ ] If is a theme, did you add the theme.css?
- Also please add a screenshot of the theme, it would be extra awesome
if you do so!
- [x] Check if any open issues are related to this PR; if so, be sure to
tag them below.
- [x] Make sure the PR title follows the Conventional Commits standard.
(https://www.conventionalcommits.org for more info)
- [x] Make sure to include your GitHub username prefixed with @ inside
parentheses at the end of the PR title.

---------

Co-authored-by: Christian Fehmer <cfe@sexy-developer.com>
Co-authored-by: Miodec <jack@monkeytype.com>

frontend/src/ts/constants/layouts.ts

@@ -210,4 +210,5 @@ export const LayoutsList:string[] = [
   "panini_wide",
   "ergopti",
   "sword",
+  "opy",
 ];

frontend/static/layouts/opy.json

@@ -0,0 +1,39 @@
+{
+  "keymapShowTopRow": false,
+  "type": "ansi",
+  "keys": {
+    "row1": [
+      "`~",
+      "1!",
+      "2\"",
+      "3§",
+      "4$",
+      "5%",
+      "6&",
+      "7/",
+      "8(",
+      "9)",
+      "0=",
+      "ß?",
+      "=+"
+    ],
+    "row2": [
+      "qQ",
+      "zZ",
+      "oO",
+      "pP",
+      "yY",
+      "wW",
+      "cC",
+      "mM",
+      "vV",
+      "ߧ",
+      "[{",
+      "]}",
+      "\\|"
+    ],
+    "row3": ["hH", "aA", "eE", "iI", "uU", "dD", "tT", "nN", "sS", "rR", "'\""],
+    "row4": ["jJ", "öÖ", "äÄ", "kK", "üÜ", "bB", "gG", "lL", "fF", "xX"],
+    "row5": [" "]
+  }
+}