chore: import upstream snapshot with attribution

tools/tree-sitter-form/test/corpus/control_flow.txt

@@ -0,0 +1,32 @@
+==================
+If statement
+==================
+
+if (count(x, 1) > 0)
+  id x = 0;
+endif;
+
+---
+
+(source_file
+  (if_statement
+    (binary_expression
+      (function_application
+        name: (identifier)
+        (identifier)
+        (number))
+      (number))
+    (substitution_statement
+      (identifier)
+      (number))))
+
+==================
+Module sort
+==================
+
+.sort
+
+---
+
+(source_file
+  (module_directive))

tools/tree-sitter-form/test/corpus/declarations.txt

@@ -0,0 +1,53 @@
+==================
+Symbol declaration
+==================
+
+Symbols a, b, c;
+
+---
+
+(source_file
+  (declaration_statement
+    (identifier)
+    (identifier)
+    (identifier)))
+
+==================
+Function declaration
+==================
+
+Functions f, g;
+
+---
+
+(source_file
+  (declaration_statement
+    (identifier)
+    (identifier)))
+
+==================
+Vector declaration
+==================
+
+Vectors p1, p2, q;
+
+---
+
+(source_file
+  (declaration_statement
+    (identifier)
+    (identifier)
+    (identifier)))
+
+==================
+Index declaration
+==================
+
+Indices mu, nu;
+
+---
+
+(source_file
+  (declaration_statement
+    (identifier)
+    (identifier)))

tools/tree-sitter-form/test/corpus/procedures.txt

@@ -0,0 +1,30 @@
+==================
+Simple procedure
+==================
+
+#procedure simplify(expr)
+  id x = 1;
+#endprocedure
+
+---
+
+(source_file
+  (procedure_definition
+    name: (identifier)
+    (identifier)
+    (substitution_statement
+      (identifier)
+      (number))))
+
+==================
+Procedure call
+==================
+
+#call simplify(result)
+
+---
+
+(source_file
+  (call_statement
+    name: (identifier)
+    (identifier)))