Improve JavaScript and CSS injection dialog

[guanglinn]

Hello, @gsantner

JavaScript and CSS injection is a powerful feature for Markor, but the experience of injection dialog is really bad.

Related issues:
#2765 - Improve the user experience of JavaScript and CSS injection dialog

In order to make it better to use, this PR implemented the following features (can greatly enhance UX):

1. Better dialog size;
2. Monospaced font;
3. Syntax highlighting (HTML, CSS and JavaScript);
4. Auto-completion (HTML, CSS and basic JavaScript);
5. Auto-indentation;
6. Code block folding;
7. Bracket and HTML tag matching;
8. Line numbers;
9. Undo redo support;
10. Reset to template code;
11. Better format for template code;
12. File Browser: Add add an option "favorite first" to FolderSortDialog.

Major features above for code editing dialog are supported by CodeMirror, which is a powerful text editor kernel.

Obsidian and GitHub are all using CodeMirror, which can proven that CodeMirror is stable enough for production.

Some great features of CodeMirror:

1. Lightweight and efficient, the size of build files for Markor is only about 500 KB;

2. Multiple code language support, see Language Support;

3. Highly customizable styles and themes extensions, see CodeMirror Styling Example;

4. Rich programming interface and extensions, see Extension;

5. Excellent performance and huge document support, see Huge Document Support: load a document with millions of lines;

6. Optimizing for mobile devices, it used platform's native selection and editing features on Android devices;

7. Strong community support;

8. LICENSE.

CodeMirror development and build guidance for Markor

Who is using CodeMirror?

See Sponsors

[guanglinn]

Screen recording

SVID_20260316_170402_1.mp4

[guanglinn]

1

Before

Now

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2

Before

Now

[guanglinn]

Dark theme

[gsantner]

Thank you @guanglinn

Major features are supported by CodeMirror: https://codemirror.net/. This is limited use of CodeMirror, it is only used in this code editing dialog. I learned that Obsidian and GitHub are all using CodeMirror, so it can be proven that CodeMirror is stable for production.

I take this with grain of salt to be honest. I know from other comments that theres a meaningful interest to move on to it - and thus to WebUI instead of the current editor solution.
For one, we did hard work to get into this shape while we still are on native sytem/Android component side. For the other, when we use the same like the others, what is the reason to use Markor then - when you could just use that other already existing tool.

[guanglinn]

@gsantner
Android component EditText is already a bottleneck of Markor in performance and functionality, especially performance.
Hope you can merge this PR, it is really great.
Not only rich features, CodeMirror's performance far exceeds EditText, you can see #2814 (comment)

[guanglinn]

I think this will be a significant milestone for Markor

[guanglinn]

Close this PR due to PR #2834 based on this branch.