docs(input): document numeric input md-maxlength validation
docs(input): document numeric input md-maxlength validation

Fixes #5321

Closes #7149

DevVersion/material,ErinCoughlan/material,robertmesserle/material,graingert/material,HipsterZipster/material,programmist/material,miguelcobain/material,ServiceManagementGroup/material,graingert/material,angular/material,gkalpak/material,programmist/material,DevVersion/material,vertazzar/material,hodeyp/material,HipsterZipster/material,vertazzar/material,ErinCoughlan/material,jadjoubran/material,hayloft/material,hayloft/material,colinskow/material,daniel-nagy/material,HarrisCorp/material,j3ski/material,daniel-nagy/material,pwistbac/material,hodeyp/material,pwistbac/material,profoundry-us/material,epelc/material,ServiceManagementGroup/material,miguelcobain/material,bluebirdtech/material,daniel-nagy/material,crisbeto/material,crisbeto/material,welkinhealth/material,HipsterZipster/material,vertazzar/material,j3ski/material,imjoeco/material,david-gang/material,david-gang/material,daniel-nagy/material,ilovett/material,welkinhealth/material,ilovett/material,Frank3K/material,SamDLT/material,miguelcobain/material,angular/material,profoundry-us/material,j3ski/material,Splaktar/material,pwistbac/material,bluebirdtech/material,marekmicek/material,Frank3K/material,gkalpak/material,gkalpak/material,imjoeco/material,Frank3K/material,clshortfuse/material,hayloft/material,dmitriz/material,HarrisCorp/material,david-gang/material,bluebirdtech/material,imjoeco/material,gkalpak/material,graingert/material,ilovett/material,dmitriz/material,angular/material,SamDLT/material,HarrisCorp/material,marekmicek/material,Frank3K/material,marekmicek/material,ilovett/material,marekmicek/material,oostmeijer/material,programmist/material,graingert/material,clshortfuse/material,Splaktar/material,DevVersion/material,dmitriz/material,crisbeto/material,jadjoubran/material,SamDLT/material,dmitriz/material,ServiceManagementGroup/material,HipsterZipster/material,colinskow/material,welkinhealth/material,SamDLT/material,hayloft/material,pwistbac/material,epelc/material,robertmesserle/material,Splaktar/material,oostmeijer/material,bluebirdtech/material,jadjoubran/material,acoreyj/material,profoundry-us/material,vertazzar/material,acoreyj/material,hodeyp/material,angular/material,colinskow/material,DevVersion/material,robertmesserle/material,robertmesserle/material,Splaktar/material,jadjoubran/material,david-gang/material,oostmeijer/material,epelc/material,crisbeto/material,welkinhealth/material,acoreyj/material,clshortfuse/material,colinskow/material,acoreyj/material,epelc/material,clshortfuse/material,ServiceManagementGroup/material,HarrisCorp/material,j3ski/material,miguelcobain/material,ErinCoughlan/material,hodeyp/material,imjoeco/material,programmist/material,ErinCoughlan/material,profoundry-us/material,oostmeijer/material