Add basics-speed module with /speed command

[JanTuck]

Adds a new basics-speed module, an EssentialsX-style feature built on the existing Basics core: the parsed command DSL and core arguments (IntRangeArg, StringOptionArg, SelectorSinglePlayerArg).

Command	Permission
/speed [walk|fly] <0-10>	basics.speed
/speed [walk|fly] <0-10> <player>	basics.speed.others

Tip

1 is the vanilla speed and decimals such as 1.5 are allowed. Without a type, the fly speed is changed while flying, otherwise the walk speed.

Notes

• Self-contained: only adds modules/basics-speed, picked up automatically by settings.gradle.kts.
• All texts are configurable in messages.yml using the shared custom tags.
• Speeds can be decimals such as 0.5 or 1.5, parsed with core's FloatRangeArg; values outside 0-10 get core's not-in-range error.
• Depends on Add FloatArg and FloatRangeArg #180 (adds FloatRangeArg); this branch is stacked on it, so the diff shows that commit until Add FloatArg and FloatRangeArg #180 is merged.
• ./gradlew :core:build :modules:basics-speed:build (compile + ktlint) passes locally on Java 17.

[mfnalex]

Why is the argument an integer instead of a float? If 1 is vanilla, then 0.5 or 1.5 etc should be possible.

[JanTuck]

Good point, there was no reason for it to be an integer. Changed in 4b26352: /speed now takes decimals in 0-10 (e.g. 0.5, 1.5), with 1 still the vanilla speed and values below 1 scaling down linearly to 0.

[JanTuck]

Follow-up: instead of a module-local argument, the float parsing now lives in core as FloatRangeArg (#180), and this branch is rebased on top of it. Same behaviour as before: 0-10 with decimals, 1 is vanilla.