rework the single-paragraph submission

By the time I'd fixed the typos in the single-paragraph PR, and clarified things to a reasonable minimal point of documentation, it's basically a new submission.

Author: pryrt

content/docs/themes.md

@@ -3,4 +3,14 @@ title: Themes
 weight: 110
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-Themes are the way to customize your background and text. You get the default. There are 20 extra themes. You can make your own theme by either by change a existing theme or make a new XML docement, whichever suits you best. Just like UGL, you can share and edit freely.
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+Themes are pre-defined sets of formatting rules, which often try to use a consistent color scheme between languages.  You may choose your theme using the [**Preferences > Style Configurator** dialog](./preferences/#style-configurator).
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+Notepad++ comes packaged with a default theme and a number of other themes to start with.  You may customize any of those themes using the Style Configurator dialog, or by editing the underlying XML files.
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+Theme XML files are stored in `%AppData%\Notepad++\Themes` for a normal installation, or in the `Themes\` subdirectory of your Notepad++ installation directory if you chose local configuration during installation or if you are using a portable version of Notepad++.  If you edit the files directly, you must exit all instances of Notepad++ and reload for the changes to take place.  (Also, if you made changes in the Style Configurator _and_ by editing the file, the two sets of changes will be in conflict, and you might not get what you want.  Stick with one method of editing at a time.)
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+To create a new theme, copy an existing theme file to a new name in the same directory, reload Notepad++, and use the Style Configurator to edit the color and font settings (or edit the XML file directly, and reload).
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+You may share a theme in a similar method to creating a new theme: copy the theme file, give it an appropriate name, and put it in your `themes\` subdirectory: it's the same whether you are sharing across multiple users on the same computer, sharing across local computers, or sharing over the internet.
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