ORC-1615: Fix Broken hyperlinks (#17)

### What changes were proposed in this pull request?

The PR aims at fixing broken hyperlinks in the ORC Format specification

### Why are the changes needed?

The changes are need to avoid 404 errors

### How was this patch tested?

Manually verified

specification/ORCv0.md

@@ -41,7 +41,7 @@ The metadata for ORC is stored using
 [Protocol Buffers](https://s.apache.org/protobuf_encoding), which provides
 the ability to add new fields without breaking readers. This document
 incorporates the Protobuf definition from the
-[ORC source code](https://github.com/apache/orc/blob/main/proto/orc_proto.proto) and the
+[ORC source code](../src/main/proto/orc/proto/orc_proto.proto) and the
 reader is encouraged to review the Protobuf encoding if they need to
 understand the byte-level encoding
 

specification/ORCv1.md

@@ -41,7 +41,7 @@ The metadata for ORC is stored using
 [Protocol Buffers](https://s.apache.org/protobuf_encoding), which provides
 the ability to add new fields without breaking readers. This document
 incorporates the Protobuf definition from the
-[ORC source code](https://github.com/apache/orc/blob/main/proto/orc_proto.proto) and the
+[ORC source code](../src/main/proto/orc/proto/orc_proto.proto) and the
 reader is encouraged to review the Protobuf encoding if they need to
 understand the byte-level encoding
 

specification/ORCv2.md

@@ -61,7 +61,7 @@ The metadata for ORC is stored using
 [Protocol Buffers](https://s.apache.org/protobuf_encoding), which provides
 the ability to add new fields without breaking readers. This document
 incorporates the Protobuf definition from the
-[ORC source code](https://github.com/apache/orc/blob/main/proto/orc_proto.proto) and the
+[ORC source code](../src/main/proto/orc/proto/orc_proto.proto) and the
 reader is encouraged to review the Protobuf encoding if they need to
 understand the byte-level encoding
 

specification/index.md

@@ -5,8 +5,8 @@ title: ORC Specification
 
 There have been two released ORC file versions:
 
-* [ORC v0](ORCv0) was released in Hive 0.11.
-* [ORC v1](ORCv1) was released in Hive 0.12 and ORC 1.x.
+* [ORC v0](ORCv0.md) was released in Hive 0.11.
+* [ORC v1](ORCv1.md) was released in Hive 0.12 and ORC 1.x.
 
 Each version of the library will detect the format version and use
 the appropriate reader. The library can also write the older versions
@@ -15,4 +15,4 @@ clusters can read correctly.
 
 We are working on a new version of the file format:
 
-* [ORC v2](ORCv2) is a work in progress and is rapidly evolving.
+* [ORC v2](ORCv2.md) is a work in progress and is rapidly evolving.