Fix Swift build cannot find src/scanner.c.

[thiezn]

Missing src/scanner.c caused compile issues within Xcode.

Updated package.swift to follow the working tree-sitter-html Package.swift format.

Example output:

ld: warning: Could not parse or use implicit file '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/SwiftUICore.framework/Versions/A/SwiftUICore.tbd': cannot link directly with 'SwiftUICore' because product being built is not an allowed client of it Undefined symbols for architecture arm64:
"_tree_sitter_css_external_scanner_create", referenced from:
_tree_sitter_css.language in TreeSitterCSS.o
"_tree_sitter_css_external_scanner_deserialize", referenced from:
_tree_sitter_css.language in TreeSitterCSS.o
"_tree_sitter_css_external_scanner_destroy", referenced from:
_tree_sitter_css.language in TreeSitterCSS.o
"_tree_sitter_css_external_scanner_scan", referenced from:
_tree_sitter_css.language in TreeSitterCSS.o
"_tree_sitter_css_external_scanner_serialize", referenced from:
_tree_sitter_css.language in TreeSitterCSS.o
"_tree_sitter_javascript_external_scanner_create", referenced from:
_tree_sitter_javascript.language in TreeSitterJavaScript.o
"_tree_sitter_javascript_external_scanner_deserialize", referenced from:
_tree_sitter_javascript.language in TreeSitterJavaScript.o
"_tree_sitter_javascript_external_scanner_destroy", referenced from:
_tree_sitter_javascript.language in TreeSitterJavaScript.o
"_tree_sitter_javascript_external_scanner_scan", referenced from:
_tree_sitter_javascript.language in TreeSitterJavaScript.o
"_tree_sitter_javascript_external_scanner_serialize", referenced from:
_tree_sitter_javascript.language in TreeSitterJavaScript.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[1024jp]

The same as tree-sitter/tree-sitter-css#90.

I’m encountering the same issue, and I’ve confirmed that this PR resolves it in my project as well.

I hope this PR will be merges.

[amaanq]

How does this fix anything? The logic is not any different, which means however you've setup the project is messing with scanner detection. The point of the code is to have generated bindings that work for grammars with and without scanners.