fix: enable strict mode

In this commit, we enable strict mode because it is required to generate correct type definition
(`.d.ts`) files. These files differ depending on whether strict mode is enabled or disabled.
Enabling strict mode allows `null|undefined` values to be provided by the parent component
(e.g., `[tp]="null"`, which should be allowed), but the compiler removes `null|undefined`
values from the binding.

We also had to patch the `@popperjs/core` types due to a mistake in their definitions.
This patch was necessary for successful compilation

package.json

@@ -5,6 +5,7 @@
     "node": "^18.19.1 || ^20.11.1 || >=22.0.0"
   },
   "scripts": {
+    "postinstall": "patch-package",
     "ng": "ng",
     "start-test": "start-server-and-test",
     "deploy": "ng deploy --base-href=https://ngneat.github.io/helipopper/",
@@ -75,6 +76,7 @@
     "karma-jasmine-html-reporter": "^1.5.0",
     "lint-staged": "^9.2.0",
     "ng-packagr": "^18.0.0",
+    "patch-package": "8.0.0",
     "prettier": "2.8.8",
     "serve": "^11.3.2",
     "standard-version": "^8.0.2",

patches/tippy.js++@popperjs+core+2.10.2.patch

@@ -0,0 +1,13 @@
+diff --git a/node_modules/tippy.js/node_modules/@popperjs/core/lib/types.d.ts b/node_modules/tippy.js/node_modules/@popperjs/core/lib/types.d.ts
+index 11f9219..f971927 100644
+--- a/node_modules/tippy.js/node_modules/@popperjs/core/lib/types.d.ts
++++ b/node_modules/tippy.js/node_modules/@popperjs/core/lib/types.d.ts
+@@ -114,7 +114,7 @@ export declare type ModifierArguments<Options extends Obj> = {
+     options: Partial<Options>;
+     name: string;
+ };
+-export declare type Modifier<Name, Options> = {
++export declare type Modifier<Name, Options extends object> = {
+     name: Name;
+     enabled: boolean;
+     phase: ModifierPhases;

projects/ngneat/helipopper/src/lib/defaults.ts

@@ -1,22 +1,22 @@
-import { TippyConfig } from './tippy.types';
+import type { TippyProps } from './tippy.types';
 
-type Variation = TippyConfig['variations'][0];
+type Variation = Partial<TippyProps>;
 
 export const tooltipVariation: Variation = {
-  theme: null,
+  theme: undefined,
   arrow: false,
   animation: 'scale',
   trigger: 'mouseenter',
-  offset: [0, 5]
+  offset: [0, 5],
 };
 
 export const popperVariation: Variation = {
   theme: 'light',
   arrow: true,
   offset: [0, 10],
-  animation: null,
+  animation: undefined,
   trigger: 'click',
-  interactive: true
+  interactive: true,
 };
 
 export function withContextMenuVariation(baseVariation: Variation): Variation {
@@ -25,6 +25,6 @@ export function withContextMenuVariation(baseVariation: Variation): Variation {
     placement: 'right-start',
     trigger: 'manual',
     arrow: false,
-    offset: [0, 0]
+    offset: [0, 0],
   };
 }