Markdown: display math through RaTeX, Mermaid through mermaid-rs-renderer, pictures from the owner's folder

Latex typesets with RaTeX to outlined SVG drawn by gpui's SvgRenderer at the
window's scale, loaded as an asset off the main thread. Diagram draws a
mermaid block in Mermaid's theme for the mode. MarkdownRenderer::base names
the folder pictures load from; data addresses decode, web ones stay unloaded.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -15,6 +15,7 @@ test-support = ["gpui/test-support", "gpui/leak-detection"]
 
 [dependencies]
 anyhow = "1"
+base64 = "0.22"
 barcoders = { version = "2", default-features = false, features = ["std"] }
 emojis = "0.9"
 futures = "0.3"
@@ -27,8 +28,13 @@ isolang = { version = "2.4", features = ["local_names", "list_languages"] }
 jiff = "0.2"
 log = "0.4"
 markdown = "=1.0.0"
+mermaid-rs-renderer = { version = "=0.3.1", default-features = false }
 pulldown-cmark = { version = "0.13", default-features = false }
 qrcode = { version = "0.14", default-features = false }
+ratex-layout = "=0.1.14"
+ratex-parser = "=0.1.14"
+ratex-svg = { version = "=0.1.14", features = ["embed-fonts"] }
+ratex-types = "=0.1.14"
 regex = "1"
 rqrr = { version = "0.11", default-features = false }
 rust-embed = "8.12"
@@ -37,6 +43,7 @@ serde_json = { version = "1", features = ["preserve_order"] }
 similar = { version = "3.2", default-features = false, features = ["std", "text", "inline", "unicode"] }
 smallvec = "1"
 unicode-segmentation = "1"
+usvg = "0.46"
 vte = { version = "0.15", default-features = false, features = ["std", "ansi"] }
 web-time = "1.1"