Support global parameters

[ficcdaf]

Problem

Key-value pairs are syntactically correct if they occur before the first section declaration. Please note that GitHub correctly highlights this snippet:

this_region="is marked as an error" 
[section name]
this_region="is no longer an error"

But the tree-sitter grammar does not, due to it returning (ERROR) nodes because it expects a named section first:

Solution

I propose modifying the grammar to make the first section header optional. Key-value pairs before the first section should still be parsed as valid nodes.

Rationale

Some dialects of ini (or, depending on the implementation) support global parameters. A key-value pair set before the first section declaration is considered to be a global parameter. Please see this specification from Apache.

The point being that it is not syntactically incorrect for an ini file to contain key-value pairs before declaring its first section. In fact, in my experience working with ini (and various ini-related) formats on Linux, many applications support global parameters.

Currently, the parser returns an error node if there is no leading section, please see this screenshot from Helix:

Crucially, the error affects the entire global section, resulting in no syntax highlighting in applications that rely on tree-sitter to provide it:

This also affects the language injection experience. For example, people often include snippets of configuration code in fenced markdown blocks. However, if the fenced code doesn't have a section, the parser gives an error node and the snippet isn't highlighted:

I think this change would greatly enhance the user experience without violating the ini specification.

[ficcdaf]

I've opened a PR that implements this feature. It doesn't break any existing tests or behavior. I look forward to discussing it with you @justinmk