Resolve a series of existing issues

[L0RD-ZER0]

This pull request aims to resolve the following:

• Resolves did you consider adding support for markdown #67
• Resolves Add threading support #72
• Resolves Add support for threaded Slack messages #73
• Resolves Does not work on ARM self hosted runners. #83
• Resolves Support for custom payload #91
• Resolves Different message depending on job.status #92
• Resolves feature: support linux/arm64 architecture #120
• Resolves message formatting, eg bold #133
• Resolves Link directly to desired workflow run attempt as opposed to summary for the given commit #142
• Resolves Enhancement: To show action failure error #150
• Resolves Thread support #157
• Resolves Update Docker file to fix mlock error #159
• Updating Readme for the new variables added
• Updating the version of Go used for compiling and Alpine used for execution