DOC: lreshape and wide_to_long references
#### Location of the documentation

* [General functions](https://pandas.pydata.org/pandas-docs/version/1.0.3/reference/general_functions.html): Does not list `lreshape`
* [DataFrame reshaping, sorting, transposing](https://pandas.pydata.org/pandas-docs/version/1.0.3/reference/frame.html#reshaping-sorting-transposing): Does not list `lreshape` or `wide_to_long`
* [pd.melt](https://pandas.pydata.org/pandas-docs/version/1.0.3/reference/api/pandas.melt.html#pandas.melt): Does not list `lreshape` or `wide_to_long` in the "See Also" section
* [pd.pivot](https://pandas.pydata.org/pandas-docs/version/1.0.3/reference/api/pandas.pivot.html): Include more related functions in the "See Also" section
* [pd.pivot_table](): Include more related functions in the "See Also" section
* [pd.wide_to_long](https://pandas.pydata.org/pandas-docs/version/1.0.3/reference/api/pandas.wide_to_long.html#pandas.wide_to_long): Does not have a "See Also" section
* [pd.lreshape](https://pandas.pydata.org/pandas-docs/version/1.0.3/reference/api/pandas.lreshape.html): _Does not exist_

#### Documentation problem

There remains an outstanding question as to whether `lreshape` and/or `wide_to_long` should be deprecated/removed (#15003). Until that question is resolved, the pandas documentation should include `lreshape` and `wide_to_long`. 

More links to and between the related pivoting/melting functions should be included in their respective "See Also" sections of their docstrings.

#### Suggested fix for documentation

Fairly self-explanatory. PR will contain the suggested additions.
