Add inlay-hint style for solarized themes. (#6327)

This uses the same color as comments, which is a light gray in both dark and light.
I think it also looks nice with italics.

runtime/themes/solarized_dark.toml

@@ -41,6 +41,7 @@
 "ui.background" = { bg = "base03" }
 
 "ui.virtual.whitespace" = { fg = "base01" }
+"ui.virtual.inlay-hint" = { fg = "base01", modifiers = ["italic"] }
 
 # 行号栏
 "ui.linenr" = { fg = "base0", bg = "base02" }

runtime/themes/solarized_light.toml

@@ -42,6 +42,7 @@
 "ui.background" = { bg = "base03" }
 
 "ui.virtual.whitespace" = { fg = "base01" }
+"ui.virtual.inlay-hint" = { fg = "base01", modifiers = ["italic"] }
 
 # 行号栏
 # line number column