Correct Plank docs

Dependencies

• [2] RQRFFUF6 Can build the first basic row
• [3] MLUGR2LL Add default impl and some basic plank logic
• [4] ES2PMPT4 Using structures instead
• [*] 5TH3AA46 10 mm extra space

Change contents

• replacement in src/main.rs at line 28
  [3.297]→[3.297:338](∅→∅)
  − /// Is this row considered complete?
  [3.297]

  [3.338]
  + /// Is this a new plank?
• replacement in src/main.rs at line 32
  [3.392]→[3.392:444](∅→∅)
  − /// Get the number of plank rows for this floor
  [3.392]

  [3.444]
  + /// Is this at the end of a row
• edit in src/main.rs at line 37
  [3.509]

  [2.0]
  + /// Return the length of the plank
• edit in src/main.rs at line 42
  [2.57]

  [3.509]
  + /// Return the original plank with the new length along with leftover