Add README files at each implementation

C#/README.md

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+# N-Queens problem using backtracking and CS
+
+## C# implementation
+
+### Set up (Ubuntu 22.04)
+
+```shell
+apt install dotnet-sdk-8.0
+```
+
+### Build
+
+```shell
+dotnet build --configuration Release queens.csproj
+```
+
+### Syntax
+
+```
+queens.jar [-test] [SIZE]
+```
+
+<dl>
+  <dt>-test</dt>
+  <dd>Enable test output.</dd>
+  <dt>SIZE</dt>
+  <dd>Length of the chess.</dd>
+</dl>
+
+### Example
+
+```
+# bin/Release/net8.0/queens 1024
+
+Queen 1: square 492
+Queen 2: square 294
+(...)
+Queen 1023: square 612
+Queen 1024: square 498
+
+Solved in 1024 steps. Time: 137 ms.
+```

C++/README.md

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+# N-Queens problem using backtracking and CS
+
+## C++ implementation
+
+### Set up (Ubuntu 22.04)
+
+```shell
+apt install g++ make
+```
+
+### Build
+
+```shell
+make
+```
+
+### Syntax
+
+```
+queens [-test] [SIZE]
+```
+
+<dl>
+  <dt>-test</dt>
+  <dd>Enable test output.</dd>
+  <dt>SIZE</dt>
+  <dd>Length of the chess.</dd>
+</dl>
+
+### Example
+
+```
+# ./queens 1024
+
+Queen 1: square 492
+Queen 2: square 294
+(...)
+Queen 1023: square 873
+Queen 1024: square 179
+
+Steps:       19019
+Discards:    906012
+Time:        476.74 ms.
+Performance: 39 steps/ms.
+             1900 discards/ms.
+```

Go/README.md

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+# N-Queens problem using backtracking and CS
+
+## Go implementation
+
+### Set up (Ubuntu 22.04)
+
+```shell
+apt install golang
+```
+
+### Build
+
+```shell
+go build
+```
+
+### Syntax
+
+```
+queens [-test] [SIZE]
+```
+
+<dl>
+  <dt>-test</dt>
+  <dd>Enable test output.</dd>
+  <dt>SIZE</dt>
+  <dd>Length of the chess.</dd>
+</dl>
+
+### Example
+
+```
+# ./queens 1024
+
+[0] 338
+[1] 591
+(...)
+[1022] 155
+[1023] 790
+Steps:       1051
+Discards:    750108
+Time:        43.254331ms
+Performance: 24 steps/ms
+```

JS/README.md

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+# N-Queens problem using backtracking and CS
+
+## JavaScript implementation
+
+### Set up (Ubuntu 22.04)
+
+```shell
+apt install nodejs
+```
+
+### Syntax
+
+```
+queens.js [-h] [-test] [SIZE]
+```
+
+<dl>
+  <dt>-h</dt>
+  <dd>Print help.</dd>
+  <dt>-test</dt>
+  <dd>Enable test output.</dd>
+  <dt>SIZE</dt>
+  <dd>Length of the chess.</dd>
+</dl>
+
+### Example
+
+```
+# java -jar queens.jar 1024
+
+Queen 1: square 172
+Queen 2: square 1003
+(...)
+Queen 1023: square 288
+Queen 1024: square 347
+
+Solved in 1020 steps. Time: 180.78 ms.
+```

Java/README.md

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+# N-Queens problem using backtracking and CS
+
+## Java implementation
+
+### Set up (Ubuntu 22.04)
+
+```shell
+apt install openjdk-19-jdk-headless
+```
+
+### Build
+
+```shell
+make
+```
+
+### Syntax
+
+```
+queens.jar [-test] [SIZE]
+```
+
+<dl>
+  <dt>-test</dt>
+  <dd>Enable test output.</dd>
+  <dt>SIZE</dt>
+  <dd>Length of the chess.</dd>
+</dl>
+
+### Example
+
+```
+# java -jar queens.jar 1024
+
+Queen 1: square 492
+Queen 2: square 294
+(...)
+Queen 1023: square 647
+Queen 1024: square 955
+
+Solved in 1142 steps. Time: 92 ms.
+```

PHP/README.md

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+# N-Queens problem using backtracking and CS
+
+## PHP implementation
+
+### Set up (Ubuntu 22.04)
+
+```shell
+apt install php
+```
+
+### Syntax
+
+```
+queens.php [-test] [SIZE]
+```
+
+<dl>
+  <dt>-test</dt>
+  <dd>Enable test output.</dd>
+  <dt>SIZE</dt>
+  <dd>Length of the chess.</dd>
+</dl>
+
+### Example
+
+```
+# php queens.php 256
+
+Queen 1: square 172
+Queen 2: square 1003
+(...)
+Queen 255: square 45
+Queen 256: square 174
+Solved in 5106 steps. Time: 445.57 ms.
+```

Python/README.md

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+# N-Queens problem using backtracking and CS
+
+## Python implementation
+
+### Set up (Ubuntu 22.04)
+
+```shell
+apt install python3
+```
+
+### Syntax
+
+```
+queens.py [-test] [SIZE]
+```
+
+<dl>
+  <dt>-test</dt>
+  <dd>Enable test output.</dd>
+  <dt>SIZE</dt>
+  <dd>Length of the chess.</dd>
+</dl>
+
+### Example
+
+```
+# ./queens.py 512
+
+Queen 1: square 172
+Queen 2: square 1003
+(...)
+Queen 511: square 1
+Queen 512: square 1
+Solved in 1591 steps. Time: 1241.388 ms.
+```