[com.sesu8642.infusion_timer] Update build steps for version 1.4.0

Required

• The app complies with the inclusion criteria
• All related fdroiddata and RFP issues have been referenced in this merge request
• Builds with fdroid build

Strongly Recommended

• The upstream app source code repo contains the app metadata (summary/description/images/changelog/etc) in a Fastlane or Triple-T folder structure
• Releases are tagged

Suggested

• External repos are added as git submodules instead of srclibs
• Multiple apks for native code

---

• add InfusionTimer 1.4.0 release
• changed display name to "Enthusiast Tea Timer"
• build uses new Flutter version from Git submodule
• added explanation for NonFreeAssets antifeature
• new regex to exclude pre-release versions