Rectify issues in BitConverter (dotnet#9778)

Author: Rageking8

xml/System/BitConverter.xml

@@ -101,7 +101,7 @@
   
  Because the return value of some methods depends on system architecture, be careful when transmitting byte data beyond machine boundaries:  
   
-- If all systems sending and receiving data are guaranteed to have the same endianness, nothing has be done to the data.  
+- If all systems sending and receiving data are guaranteed to have the same endianness, nothing has to be done to the data.  
   
 - If systems sending and receiving data can have different endianness, always transmit data in a particular order. This means that the order of bytes in the array may have to be reversed either before sending them or after receiving them. A common convention is to transmit data in network byte order (big-endian order). The following example provides an implementation for sending an integer value in network byte order.  
   
@@ -1898,7 +1898,7 @@
       <Docs>
         <param name="value">An array of bytes that includes the two bytes to convert.</param>
         <param name="startIndex">The starting position within <paramref name="value" />.</param>
-        <summary>Returns a laft-precision floating point number converted from two bytes at a specified position in a byte array.</summary>
+        <summary>Returns a half-precision floating point number converted from two bytes at a specified position in a byte array.</summary>
         <returns>A half-precision floating point number formed by two bytes beginning at <paramref name="startIndex" />.</returns>
         <remarks>To be added.</remarks>
         <exception cref="T:System.ArgumentException">