Add a guide for adding custom themes

docs/cloudtube/Adding custom themes.md

@@ -0,0 +1,47 @@
+## Adding custom themes to CloudTube
+
+#### NOTE: This file uses `custom` as the name of the custom theme, but it can be whatever you like, just make sure to stay consistent across all steps
+
+1. Copy `sass/themes/_dark.scss` (or whatever base you prefer) into `sass/themes/_custom.scss`
+
+2. Edit the new file by setting the colors you want the custom theme to use
+
+3. Make a new file called `sass/custom.sass` and put
+```sass
+@use "themes/custom" as *
+@use "includes/main" with ($_theme: $theme)
+```
+in it, optionally add
+```sass
+@use "theme-modules/edgeless" with ($_theme: $theme)
+```
+if you want to hide borders around the navigation bar and recommended videos list
+
+4. Edit `server.js` and add a new entry at line 28:
+```js
+...
+server.addRoute("/static/css/edgeless-light.css", "sass/edgeless-light.sass", "sass")
+server.addRoute("/static/css/custom.css", "sass/custom.sass", "sass")
+...
+```
+
+5. Edit `pug/settings` and add a new entry at line 46:
+```pug
+...
+{value: "2", text: "Edgeless light"},
+{value: "3", text: "Custom"}
+...
+```
+This will be the name shown in the settings menu when you go to select it, make sure to put a comma at the end of the previous entry (line 45)
+
+6. Edit `pug/includes/layout.pug` and append the name of the theme in the array on line 6:
+```pug
+...
+ - const theme = settings && ["dark", "light", "edgeless-light", "custom"][settings.theme] || "dark"
+...
+```
+This must be the same name you put in steps 1 and 3
+
+7. Restart CloudTube
+
+That's it, enjoy your snazzy new theme!