Add local fork of meteor-reactive-cache package

- Clone @wekanteam/meteor-reactive-cache to npm-packages/
- Add .meteorignore to exclude npm-packages from Meteor
- Update package.json to use local file path

This allows direct modification of the package for Meteor 3.0
async migration while maintaining publishability to npm.

npm-packages/meteor-reactive-cache/src/ReactiveCache.js

@@ -0,0 +1,56 @@
+import Tracker from './meteor/tracker';
+
+export default class ReactiveCache {
+  constructor(compare, shouldStop) {
+    this.shouldStop = shouldStop || (() => true);
+    this.compare = compare || ((a, b) => a === b);
+    this.values = {};
+    this.deps = {};
+  }
+
+  ensureDependency(key) {
+    if (!this.deps[key]) this.deps[key] = new Tracker.Dependency();
+    return this.deps[key];
+  }
+
+  checkDeletion(key) {
+    const dep = this.ensureDependency(key);
+    if (dep.hasDependents()) return false;
+    delete this.values[key];
+    delete this.deps[key];
+    return true;
+  }
+
+  clear() {
+    Object.keys(this.values).forEach((key) => this.del(key));
+  }
+
+  del(key) {
+    const dep = this.ensureDependency(key);
+    delete this.values[key];
+    if (this.checkDeletion(key)) return;
+    dep.changed();
+  }
+
+  set(key, data, bypassCompare) {
+    const dep = this.ensureDependency(key);
+    const current = this.values[key];
+    this.values[key] = data;
+    if (!this.compare(current, data) || bypassCompare) {
+      dep.changed();
+    }
+  }
+
+  get(key) {
+    const data = this.values[key];
+    if (Tracker.currentComputation) {
+      const dep = this.ensureDependency(key);
+      dep.depend();
+      Tracker.currentComputation.onStop(() => {
+        if (!this.shouldStop(key)) return;
+        this.checkDeletion(key);
+      });
+    }
+    return data;
+  }
+}