(Obsidian Plugin) Allow spellcheck based on YAML property

**What problem does this solve?**
Disable checking of non-english obsidian files

**Proposed Solution**
Allow disabling the spellchecking of files based on more than filename/location, for instance checking the value of a certain YAML property

**Examples**
Include only files with property: "language" = "english"

**Component**
- Plugin (Obsidian)

Start by locating the Obsidian plugin implementation and its existing filename or location-based spellcheck configuration. Trace how a YAML property could control whether a file is checked, then verify the example behavior: files with language set to english are included while non-English files can be skipped.

Written by the indexing model from the issue text.