Sayboard: add new app at v4.0.2

Required

• The app complies with the inclusion criteria
• The original app author has been notified (and does not oppose the inclusion)
• 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
• Enable Reproducible Builds
• Multiple apks for native code

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First time contributor here. Some remaining questions:

• The license is GPL-3.0 but unclear if -only or -or-later variant. I asked the developer here.
• Is it okay to use an app id without owning the domain for it?
• A universal and multiple architecture-specific APKs are emitted. Do I have to add multiple Builds, one for each architecture? For now, I opted to use the universal APK.
• The build depends on this merged PR, therefore it is no "clean" version code.
• The app needs speech databases, which are downloaded on runtime. Do you need a proper privacy policy?
• I have no idea whether the native stuff is compiled from source. I guess the CI/scanner will catch this.