Revert "Change documentation titles to sentence-case"

This reverts commit e5bef3c.

Author: kalaiyarasiganeshalingam

README.md

@@ -15,15 +15,15 @@ character strings. If a particular string is in the set described by a regular e
 
 For a quick sample on demonstrating the usage, see [Ballerina By Examples](https://ballerina.io/learn/by-example/).
 
-## Issues and projects
+## Issues and Projects
 
 The **Issues** and **Projects** tabs are disabled for this repository as this is part of the Ballerina Standard Library. To report bugs, request new features, start new discussions, view project boards, etc., go to the Ballerina Standard Library [parent repository](https://github.com/ballerina-platform/ballerina-standard-library). 
 
 This repository contains only the source code of the package.
 
-## Build from the source
+## Building from the Source
 
-### Set up the prerequisites
+### Setting Up the Prerequisites
 
 * Download and install Java SE Development Kit (JDK) version 11 (from one of the following locations).
 
@@ -33,9 +33,9 @@ This repository contains only the source code of the package.
 
         > **Note:** Set the JAVA_HOME environment variable to the path name of the directory into which you installed JDK.
 
-### Build the source
+### Building the Source
 
-Execute the commands below to build from the source.
+Execute the commands below to build from source.
 
 1. To build the library:
 
@@ -69,17 +69,17 @@ Execute the commands below to build from the source.
 
         ./gradlew clean build -PpublishToCentral=true
         
-## Contribute to Ballerina
+## Contributing to Ballerina
 
 As an open source project, Ballerina welcomes contributions from the community. 
 
 For more information, go to the [contribution guidelines](https://github.com/ballerina-platform/ballerina-lang/blob/master/CONTRIBUTING.md).
 
-## Code of conduct
+## Code of Conduct
 
 All contributors are encouraged to read the [Ballerina Code of Conduct](https://ballerina.io/code-of-conduct).
 
-## Useful links
+## Useful Links
 
 * For more information go to the [`regex` library](https://lib.ballerina.io/ballerina/regex/latest).
 * For example demonstrations of the usage, go to [Ballerina By Examples](https://ballerina.io/learn/by-example/).

ballerina/Package.md

@@ -1,16 +1,16 @@
-## Package overview
+## Package Overview
 
 This module provides APIs for searching, splitting, and replacing the set of characters of a string. These APIs are using a
 regular expression as a `String` to perform these operations by finding the string matches.
 
 [Regular expressions](https://en.wikipedia.org/wiki/Regular_expression), are notations for describing sets of
 character strings. If a particular string is in the set described by a regular expression, the regular expression matches that string.
 
-## Report issues
+## Report Issues
 
 To report bugs, request new features, start new discussions, view project boards, etc., go to the [Ballerina standard library parent repository](https://github.com/ballerina-platform/ballerina-standard-library).
 
-### Useful links
+### Useful Links
 
 - Chat live with us via our [Slack channel](https://ballerina.io/community/slack/).
 - Post all technical questions on Stack Overflow with the [#ballerina](https://stackoverflow.com/questions/tagged/ballerina) tag.