Update Alpine Base Image and Fix Keyword Casing - 0x07cb patch 1

[0x07CB]

Correction of Keyword Casing in the Dockerfile

This PR fixes a warning generated by Docker during the image build. The keyword as used in the instruction FROM ... as builder has been replaced with uppercase AS to ensure consistency with best practices and to avoid the FromAsCasing warning.

[0x07CB]

Update Alpine Base Image and Fix Keyword Casing

This pull request contains two commits:

• The first one fixes an inconsistency in the casing of the AS keyword in the FROM instruction of the Dockerfile, preventing the FromAsCasing warning and ensuring better readability.
• The second updates the Alpine base image from version 3.9 to 3.13.19. This change enhances security and compatibility by using a more recent version, benefiting from patches and improvements while ensuring optimal support for dependencies required for compiling and running endlessh.