Apply Flutter best practices [Non-Breaking] (#2)

* Add flutter_lints package

* Use key in widget constructors

lint: use_key_in_widget_constructors

* Unnecessary new keyword

lint: unnecessary_new

* Prefer const with constant constructors

* Exclude protobuf files from analyzer

* Private field could be final

* Annotate overridden members

* Use initializing formals when possible

* Don't access members with `this` unless avoiding shadowing

* Prefer is! operator

* Use isEmpty instead of length

* Use collection literals when possible

* Revert comment changes

* Cleaner null testing

* Misc fixes

* Avoid using `forEach` with a function literal

* Prefer `final` over `var` where applicable

* Enforce stricter type-checking

* Ignore VS Code files

* Flutter format

* Prefer using lowerCamelCase for constant names

* flutter format -l 100

* Disable `avoid_print` for examples

* Slight improvements to example

Should solve lint error: no_logic_in_create_state

example/pubspec.lock

@@ -90,6 +90,13 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_lints:
+    dependency: "direct dev"
+    description:
+      name: flutter_lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.4"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -116,6 +123,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "4.0.0"
+  lints:
+    dependency: transitive
+    description:
+      name: lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
   livekit_client:
     dependency: "direct main"
     description:
@@ -171,14 +185,14 @@ packages:
       name: path_provider_linux
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.0.2"
   path_provider_macos:
     dependency: transitive
     description:
       name: path_provider_macos
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.0.2"
   path_provider_platform_interface:
     dependency: transitive
     description:
@@ -192,7 +206,7 @@ packages:
       name: path_provider_windows
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.1"
+    version: "2.0.3"
   pedantic:
     dependency: transitive
     description:
@@ -206,7 +220,7 @@ packages:
       name: platform
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.0.0"
+    version: "3.0.2"
   plugin_platform_interface:
     dependency: transitive
     description:
@@ -220,7 +234,7 @@ packages:
       name: process
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.2.1"
+    version: "4.2.3"
   protobuf:
     dependency: transitive
     description:
@@ -330,7 +344,7 @@ packages:
       name: win32
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.5"
+    version: "2.2.7"
   xdg_directories:
     dependency: transitive
     description:
@@ -340,4 +354,4 @@ packages:
     version: "0.2.0"
 sdks:
   dart: ">=2.13.0 <3.0.0"
-  flutter: ">=1.22.0"
+  flutter: ">=2.0.0"