Fixing "No such file or directory" for manifest.json for docker users

[koseduhemak]

Fixing "No such file or directory: 'custom_components/better_thermostat/manifest.json': could not read version from manifest file." for docker users.

Motivation:

Eversince my homeassistant log shows the following:
2023-11-03 14:55:13.885 ERROR (MainThread) [custom_components.better_thermostat.const] better_thermostat [Errno 2] No such file or directory: 'custom_components/better_thermostat/manifest.json': could not read version from manifest file.

This is annoying, so I fixed it by resolving the path to manifest.json inside the const.py.

Changes:

Using relativ-to-current-file path discovery for manifest.json.

Related issue (check one):

• fixes #
• [x ] there is no related issue ticket

Checklist (check one):

• I did not change any code (e.g. documentation changes)
• [ x ] The code change is tested and works locally.

Test-Hardware list (for code changes)

HA Version: 2023.11.0 (using this container: https://docs.linuxserver.io/images/docker-homeassistant/#usage)
Zigbee2MQTT Version: 1.33.2 commit: 9996c93
TRV Hardware: SEA801-Zigbee/SEA802-Zigbee
HACS 1.33.0
BetterThermostat 1.4.0

New device mappings

N/A

[koseduhemak]

just reprocessed the const.py with pre-commit to be consistent with sensible defaults in this repo.