Add CHANGELOG for 0.48.0

[alamb]

Part of #1296

Prepare CHANGELOG for 0.48.0 release.

I am waiting for a few more PRs to potentially merge before finalizing and merging this PR

[coveralls]

Pull Request Test Coverage Report for Build 9857488210

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1599 unchanged lines in 7 files lost coverage.
• Overall coverage increased (+0.01%) to 89.187%

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Files with Coverage Reduction	New Missed Lines	%
tests/sqlparser_mssql.rs	25	92.92%
src/ast/ddl.rs	58	86.18%
src/ast/query.rs	90	85.51%
tests/sqlparser_postgres.rs	255	87.99%
src/parser/mod.rs	255	93.29%
src/ast/mod.rs	268	81.39%
tests/sqlparser_common.rs	648	89.65%

Totals
Change from base Build 9838850938:	0.01%
Covered Lines:	26781
Relevant Lines:	30028

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💛 - Coveralls