Fix docs

README.md

@@ -31,6 +31,8 @@ The package provides:
 
 ## Installation
 
+The package could be installed with [Composer](https://getcomposer.org):
+
 ```shell
 composer require yiisoft/strings
 ```
@@ -241,46 +243,12 @@ if ($regexp->matches('second')) {
 }
 ```
 
-## Testing
-
-### Unit testing
-
-The package is tested with [PHPUnit](https://phpunit.de/). To run tests:
-
-```shell
-./vendor/bin/phpunit
-```
-
-### Mutation testing
-
-The package tests are checked with [Infection](https://infection.github.io/) mutation framework with
-[Infection Static Analysis Plugin](https://github.com/Roave/infection-static-analysis-plugin). To run it:
-
-```shell
-./vendor/bin/roave-infection-static-analysis-plugin
-```
-
-### Static analysis
-
-The code is statically analyzed with [Psalm](https://psalm.dev/). To run static analysis:
-
-```shell
-./vendor/bin/psalm
-```
-
-### Code style
-
-Use [Rector](https://github.com/rectorphp/rector) to make codebase follow some specific rules or
-use either newest or any specific version of PHP:
-
-```shell
-./vendor/bin/rector
-```
+## Documentation
 
-### Dependencies
+- [Internals](docs/internals.md)
 
-Use [ComposerRequireChecker](https://github.com/maglnet/ComposerRequireChecker) to detect transitive
-[Composer](https://getcomposer.org/) dependencies.
+If you need help or have a question, the [Yii Forum](https://forum.yiiframework.com/c/yii-3-0/63) is a good place for that.
+You may also check out other [Yii Community Resources](https://www.yiiframework.com/community).
 
 ## License
 

UPGRADE.md

@@ -1,12 +1,16 @@
-# Upgrading Instructions
+# Yii Strings Upgrading Instructions
 
 These notes highlight changes that could break your application when you upgrade package from one version to another.
 
 Upgrading in general is as simple as updating your dependency in your `composer.json` and running `composer update`.
 In a big application however there may be more things to consider, which are explained in the following.
 
-> Note: The following upgrading instructions are cumulative. That is, if you want to upgrade from a version A to version
-> C and there is a version B between A and C, you need to follow the instructions for both A and B.
+> **!!!IMPORTANT!!!**
+>
+> The following upgrading instructions are *cumulative*. That is,
+> if you want to upgrade from version A to version C and there is
+> version B between A and C, you need to following the instructions
+> for both A and B.
 
 ## Upgrade from 1.2.0
 

docs/internals.md

@@ -0,0 +1,45 @@
+# Internals
+
+## Unit testing
+
+The package is tested with [PHPUnit](https://phpunit.de/). To run tests:
+
+```shell
+./vendor/bin/phpunit
+```
+
+## Mutation testing
+
+The package tests are checked with [Infection](https://infection.github.io/) mutation framework with
+[Infection Static Analysis Plugin](https://github.com/Roave/infection-static-analysis-plugin). To run it:
+
+```shell
+./vendor/bin/roave-infection-static-analysis-plugin
+```
+
+## Static analysis
+
+The code is statically analyzed with [Psalm](https://psalm.dev/). To run static analysis:
+
+```shell
+./vendor/bin/psalm
+```
+
+## Code style
+
+Use [Rector](https://github.com/rectorphp/rector) to make codebase follow some specific rules or
+use either newest or any specific version of PHP:
+
+```shell
+./vendor/bin/rector
+```
+
+## Dependencies
+
+This package uses [composer-require-checker](https://github.com/maglnet/ComposerRequireChecker) to check if all dependencies are correctly defined in `composer.json`.
+
+To run the checker, execute the following command:
+
+```shell
+./vendor/bin/composer-require-checker
+```