Add StringBuilder & Markdown extensions (#206)

In this PR, I have added StringBuilder extensions to avoid `.Append`
reuse such as `.Append("- ").AppendLine()`

Closes #205

---------

Signed-off-by: mctaylors <cantsendmails@mctaylors.ru>

src/Extensions/MarkdownExtensions.cs

@@ -0,0 +1,16 @@
+namespace Octobot.Extensions;
+
+public static class MarkdownExtensions
+{
+    /// <summary>
+    /// Formats a string to use Markdown Bullet formatting.
+    /// </summary>
+    /// <param name="text">The input text to format.</param>
+    /// <returns>
+    /// A markdown-formatted bullet string.
+    /// </returns>
+    public static string BulletPoint(string text)
+    {
+        return $"- {text}";
+    }
+}

src/Extensions/StringBuilderExtensions.cs

@@ -0,0 +1,62 @@
+using System.Text;
+
+namespace Octobot.Extensions;
+
+public static class StringBuilderExtensions
+{
+    /// <summary>
+    ///     Appends the input string with Markdown Bullet formatting to the specified <see cref="StringBuilder" /> object.
+    /// </summary>
+    /// <param name="builder">The <see cref="StringBuilder" /> object.</param>
+    /// <param name="value">The string to append with bullet point.</param>
+    /// <returns>
+    ///     The builder with the appended string with Markdown Bullet formatting.
+    /// </returns>
+    public static StringBuilder AppendBulletPoint(this StringBuilder builder, string? value)
+    {
+        return builder.Append("- ").Append(value);
+    }
+
+    /// <summary>
+    ///     Appends the input string with Markdown Sub-Bullet formatting to the specified <see cref="StringBuilder" /> object.
+    /// </summary>
+    /// <param name="builder">The <see cref="StringBuilder" /> object.</param>
+    /// <param name="value">The string to append with sub-bullet point.</param>
+    /// <returns>
+    ///     The builder with the appended string with Markdown Sub-Bullet formatting.
+    /// </returns>
+    public static StringBuilder AppendSubBulletPoint(this StringBuilder builder, string? value)
+    {
+        return builder.Append(" - ").Append(value);
+    }
+
+    /// <summary>
+    ///     Appends the input string with Markdown Bullet formatting followed by
+    ///     the default line terminator to the end of specified <see cref="StringBuilder" /> object.
+    /// </summary>
+    /// <param name="builder">The <see cref="StringBuilder" /> object.</param>
+    /// <param name="value">The string to append with bullet point.</param>
+    /// <returns>
+    ///     The builder with the appended string with Markdown Bullet formatting
+    ///     and default line terminator at the end.
+    /// </returns>
+    public static StringBuilder AppendBulletPointLine(this StringBuilder builder, string? value)
+    {
+        return builder.Append("- ").AppendLine(value);
+    }
+
+    /// <summary>
+    ///     Appends the input string with Markdown Sub-Bullet formatting followed by
+    ///     the default line terminator to the end of specified <see cref="StringBuilder" /> object.
+    /// </summary>
+    /// <param name="builder">The <see cref="StringBuilder" /> object.</param>
+    /// <param name="value">The string to append with sub-bullet point.</param>
+    /// <returns>
+    ///     The builder with the appended string with Markdown Sub-Bullet formatting
+    ///     and default line terminator at the end.
+    /// </returns>
+    public static StringBuilder AppendSubBulletPointLine(this StringBuilder builder, string? value)
+    {
+        return builder.Append(" - ").AppendLine(value);
+    }
+}