Have our own reference pages instead of links.

[mjonss]

Change Request

Please answer the following questions before submitting your issue. Thanks!

1. Describe what you find is inappropriate or missing in the existing docs. In the functions-and-operators directory, there are many pages that simply uses a link to dev.mysql.com/doc/refman/... instead of explaining the function/operator in our own documentation. This also causes a dependency on an external resource.

2. Describe your suggestion or addition. Create content describing the various functions and operators in TiDB, instead of simply linking to the mysql reference manual.

3. Provide some reference materials (such as documents and websites) if you could.

$  git grep 'dev.mysql.com.*refman' | cut -d: -f1 | uniq -c | sort -n -r
  75 functions-and-operators/operators.md
  62 functions-and-operators/date-and-time-functions.md
  59 functions-and-operators/string-functions.md
  38 functions-and-operators/numeric-functions-and-operators.md
  35 functions-and-operators/json-functions.md
  19 functions-and-operators/miscellaneous-functions.md
  13 functions-and-operators/information-functions.md
  12 functions-and-operators/window-functions.md
  12 functions-and-operators/encryption-and-compression-functions.md
  12 functions-and-operators/aggregate-group-by-functions.md
  11 functions-and-operators/expressions-pushed-down.md
   8 functions-and-operators/bit-functions-and-operators.md