v5.1.1 : support ldmx-sw as container-home

Without breaking current configurations where the container-home is the parent directory of ldmx-sw (aka LDMX_BASE), I added support for having the container-home be ldmx-sw itself in #138

Additionally, I removed the custom-Geant4 scripting from ldmx-env-init.sh in favor of documenting it on the webiste. This means the following environment variables that perviously were used to tune the in-container environment will be silently ignored.

• LDMX_CUSTOM_GEANT4
• LDMX_CUSTOM_GEANT4_CONFIRM_DEV
• LDMX_CUSTOM_GEANT4_DATA_DIR

See the updated site page on Custom Geant4 for details on how to run with a custom build of Geant4. Its basically just putting the shell scripting that previously was in the image into your local copy of .profile residing within the container-home directory.

Besides this, I also did some minor updates to the docs following @EBerzin testing with a custom Acts build in #134

🤖 Bot Changes

• Auto ldmx-sw Version Update by @github-actions[bot] in #131
• Auto ldmx-sw Version Update by @github-actions[bot] in #132
• Auto ldmx-sw Version Update by @github-actions[bot] in #133
• Auto ldmx-sw Version Update by @github-actions[bot] in #135
• Auto ldmx-sw Version Update by @github-actions[bot] in #136

Full Changelog: v5.1.0...v5.1.1