MINOR: Add summary table of encodings and supported types (in Encodings.md) (#550) (#552)

* MINOR: Add summary table of encodings and supported types (in Encodings.md) (#550)

* MINOR: Add summary table of encodings and supported types (in Encodings.md) (#550);

* MINOR: Add summary table of encodings and supported types (in Encodings.md) (#550) - remove v1 related column, and seperate tables for supported and deprecated encodings

* Update Encodings.md

Add Dictionary indices to encoding targets

Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

* Update Encodings.md

fix typo

Co-authored-by: Gang Wu <ustcwg@gmail.com>

* added note/link to the implementation status page

---------

Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>
Co-authored-by: Gang Wu <ustcwg@gmail.com>

Author: 3 people

Encodings.md

@@ -25,6 +25,27 @@ This file contains the specification of all supported encodings.
 Unless otherwise stated in page or encoding documentation, any encoding can be
 used with any page type.
 
+### Supported Encodings
+
+For details on current implementation status, see the [Implementation Status](https://parquet.apache.org/docs/file-format/implementationstatus/#encodings) page.
+
+| Encoding type                                    | Encoding enum                                             | Supported Types                                   |
+| ------------------------------------------------ | --------------------------------------------------------- | ------------------------------------------------- |
+| [Plain](#PLAIN)                                  | PLAIN = 0                                                 | All Physical Types                                |
+| [Dictionary Encoding](#DICTIONARY)               | PLAIN_DICTIONARY = 2 (Deprecated) <br> RLE_DICTIONARY = 8 | All Physical Types                                |
+| [Run Length Encoding / Bit-Packing Hybrid](#RLE) | RLE = 3                                                   | BOOLEAN, Dictionary Indices                       |
+| [Delta Encoding](#DELTAENC)                      | DELTA_BINARY_PACKED = 5                                   | INT32, INT64                                      |
+| [Delta-length byte array](#DELTALENGTH)          | DELTA_LENGTH_BYTE_ARRAY = 6                               | BYTE_ARRAY                                        |
+| [Delta Strings](#DELTASTRING)                    | DELTA_BYTE_ARRAY = 7                                      | BYTE_ARRAY, FIXED_LEN_BYTE_ARRAY                  |
+| [Byte Stream Split](#BYTESTREAMSPLIT)            | BYTE_STREAM_SPLIT = 9                                     | INT32, INT64, FLOAT, DOUBLE, FIXED_LEN_BYTE_ARRAY |
+
+### Deprecated Encodings
+
+| Encoding type                         | Encoding enum  |
+| ------------------------------------- | -------------- |
+| [Bit-packed (Deprecated)](#BITPACKED) | BIT_PACKED = 4 |
+
+
 <a name="PLAIN"></a>
 ### Plain: (PLAIN = 0)
 
@@ -50,6 +71,7 @@ For native types, this outputs the data as little endian. Floating
 For the byte array type, it encodes the length as a 4 byte little
 endian, followed by the bytes.
 
+<a name="DICTIONARY"></a>
 ### Dictionary Encoding (PLAIN_DICTIONARY = 2 and RLE_DICTIONARY = 8)
 The dictionary encoding builds a dictionary of values encountered in a given column. The
 dictionary will be stored in a dictionary page per column chunk. The values are stored as integers
@@ -295,6 +317,7 @@ The encoded data is
 This encoding is similar to the [RLE/bit-packing](#RLE) encoding. However the [RLE/bit-packing](#RLE) encoding is specifically used when the range of ints is small over the entire page, as is true of repetition and definition levels. It uses a single bit width for the whole page.
 The delta encoding algorithm described above stores a bit width per miniblock and is less sensitive to variations in the size of encoded integers. It is also somewhat doing RLE encoding as a block containing all the same values will be bit packed to a zero bit width thus being only a header.
 
+<a name="DELTALENGTH"></a>
 ### Delta-length byte array: (DELTA_LENGTH_BYTE_ARRAY = 6)
 
 Supported Types: BYTE_ARRAY
@@ -317,6 +340,7 @@ then the encoded data would be comprised of the following segments:
 - DeltaEncoding(5, 5, 6, 6) (the string lengths)
 - "HelloWorldFoobarABCDEF"
 
+<a name="DELTASTRING"></a>
 ### Delta Strings: (DELTA_BYTE_ARRAY = 7)
 
 Supported Types: BYTE_ARRAY, FIXED_LEN_BYTE_ARRAY
@@ -338,6 +362,7 @@ then the encoded data would be comprised of the following segments:
 
 Note that, even for FIXED_LEN_BYTE_ARRAY, all lengths are encoded despite the redundancy.
 
+<a name="BYTESTREAMSPLIT"></a>
 ### Byte Stream Split: (BYTE_STREAM_SPLIT = 9)
 
 Supported Types: FLOAT, DOUBLE, INT32, INT64, FIXED_LEN_BYTE_ARRAY