add an example to compute matrix ranks

this MR

• implements the Display trait for Matrix to allow to show it
• makes from_vec_vec and rank public
• add rank.rs

example

Note

• this has been run with Nushell
• a -1 is an impossible value and thus will generate a random element instead

cargo run --example rank -- ...[
    "1,0,-1"
    "0,0,-1"
    "0,1,-1"
    "0,0,-1"
    "0,0,-1"
]

will output

/1 0 314995448938783965509764369801440879676\
|0 0 236699644179594774251145667390896459418|
|0 1 187004145196223910655928022134499908037|
|0 0 273500202756822505549423242088598868403|
\0 0 286599222098418496365691949902317095505/

m: 5
n: 3
r: 5