Enable level name to be displayed in status_line

[angilbert]

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• I have searched the tracker for similar issues (including closed ones)
• I have provided a detailed example for how this feature should work
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This is related to #79 - so could be considered at the same time.

I think it would be super useful in many games if the level-name could be easily displayed on/below the level when it loads. One possible approach would be to make this the default behaviour of status_line (if enabled - and assuming the level has a name). At the moment it is only possible to display a level-name by giving every level some sort of unique signature within the level-design and then having a hard-coded rule (one for EVERY level) to update the status-bar. Which is extremely impractical. The example below illustrates how it could be achieved using a single rule (if LevelName was a reserved keyword that could be utilised in a rule). However a new prelude option to always display the level name in the status bar (on level load) would be a very easy approach and would require no additional rule(s) at all.

A further extension would be to allow the level name to be utilised as a text-string for a canvas text-area - but I think that would be less useful and much harder to implement.

[angilbert]

It should be noted this could only be utilised by games made from a series of atomic levels and therefore wouldn't be compatible with an open-world type game (which typically has one huge level). A point to emphasise in the documentation perhaps.