editorconfig: unofficial max_line_length key is supported

[muzimuzhi]

Biome supports max_line_width key used in .editorconfig (78d70d2), but actually max_line_width is not officially supported by EditorConfig. Maybe Biome should drop support for it.

The commit message of benesch/materialize@31f2d7f can be used as a good summary:

The max_line_length directive is not officially part of the EditorConfig
spec, and its current implementations have been contentious [0] [1]. The
tl;dr is that it is not clear whether to use max_line_length for soft
wrapping, hard wrapping, or just a visual display of a ruler, and
various tools and editors have different opinions.

Related discussions in editorconfig repos:

• Property research: maximum line length | wiki
• New property: rulers editorconfig/editorconfig#89
• Implement max_line_length editorconfig/editorconfig-vscode#53
• Deprecate max_line_length in favor of rulers editorconfig/editorconfig#387