feat(nvim): re-add projectionist.vim

Re-add `projectionist.vim` with a minimal configuration for setting the
alternate file in basic PHP library or TypeScript projects.

after/plugin/projectionist.lua

@@ -0,0 +1,42 @@
+vim.g.projectionist_heuristics = {
+  ["composer.json"] = {
+    ["src/*.php"] = {
+      type = "source",
+      alternate = "tests/{}Test.php",
+    },
+
+    ["src/Controller/*.php"] = {
+      type = "controller",
+    },
+
+    ["src/Model/*.php"] = {
+      type = "model",
+    },
+
+    ["src/Service/*.php"] = {
+      type = "service",
+    },
+
+    ["tests/*Test.php"] = {
+      type = "test",
+      alternate = "src/{}.php",
+    },
+  },
+
+  ["package.json"] = {
+    ["src/*.ts"] = {
+      type = "source",
+      alternate = "tests/{}.test.ts",
+    },
+
+    ["src/*.service.ts"] = {
+      type = "source",
+      alternate = "tests/{}.test.ts",
+    },
+
+    ["tests/*.test.ts"] = {
+      type = "test",
+      alternate = "src/{}.ts",
+    },
+  },
+}