Fixes for the documentation of the TextCatalog

[sfilipi]

TokenizeIntoCharactersAsKeys:

• The description of TokenizingByCharactersEstimator should be corrected to:
  "Create a TokenizingByCharactersEstimator, which tokenizes words by splitting text into sequences of
  characters using a sliding window."
• outputColumnName description should state that the outputs are Uints rather than keys? I think it might confuse the users that those are KeyDataViewTypes. Or should the name of this method be changed? @artidoro @Ivanidzo4ka @zeahmed ?
  "Name of the column resulting from the transformation of inputColumnName. This column's data type will be a variable-sized vector of Uint".
• useMarkerCharacters needs a better description.

RemoveStopWords

• inputColumnName,:
  "This estimator operates over a vector of text.

CustomStopWordsRemovingEstimator

• Output column data type
  "Variable-sized vector of Text"
  Replace Unknown-sized vector with Variable-sized vector.
• xref not resolving:
  xref:Microsoft.ML.Transforms.Text.CustomStopWordsRemovingTransformer/

WordHashBagEstimator

• Output column data type
  Known-size vector of of Single
• Replace metadata with annotations in the documentation references.

NgramHashingEstimator

• broken xref:Microsoft.ML.Transforms.Text.NgramHashingTransformer/ link.
• casing: "in a way that the former takes "

NormalizeText

• outputColumnName
  "This column's data type is a scalar of text or "

WordEmbeddingEstimator

• Add links for Glove50D, dimensionality of the embedding model used.
• Re-phrasehere and everywhere: See the See Also section for links to usage examples.

[Ivanidzo4ka]

outputColumnName description should state that the outputs are Uints rather than keys? I think it might confuse the users that those are KeyDataViewTypes. Or should the name of this method be changed? @artidoro @Ivanidzo4ka @zeahmed ?

TokenizeIntoCharactersAsKeys It has keys in the name, and Key is not always UInt, it can be any unsign type. This is not the only transform which has Keys and I don't have problem with Key type. Still better than UInt.

[sfilipi]

Closed wit #3570