docs: Add latest changes to 1.0 changelog

Signed-off-by: Jussi Kukkonen <[email protected]>

docs/CHANGELOG.md

@@ -18,16 +18,17 @@ in `tuf.api` or `tuf.ngclient`.
   #1836)
 * Metadata API: Update supported spec version to "1.0.28" (#1825)
 * Metadata API: Accept legacy spec version "1.0" (#1796)
+* Metadata API: Accept custom fields in Metadata (#1861)
 * ngclient: Remove temporary file in failure cases (#1757)
 * ngclient: Explicitly encode rolename in URL (#1759)
 * ngclient: Allow HTTP payload compression (#1774)
 * ngclient: Make exceptions more consistent (#1799, #1810)
 * docs: Improve documentation (#1744, #1749, #1750, #1755, #1771, #1776, #1772,
-  #1780, #1781, #1800, #1815, #1820, #1829, #1838, #1850, #1855)
+  #1780, #1781, #1800, #1815, #1820, #1829, #1838, #1850, #1853, #1855, #1856)
 * build: Various build infrastructure improvements (#1718, #1724, #1760, #1762,
   #1767, #1803, #1830, #1832, #1837, #1839)
 * build: Stop supporting EOL Python 3.6 (#1783)
-* build: Update dependencies (#1827, #1834)
+* build: Update dependencies (#1809, #1827, #1834, #1863, #1865)
 
 ### Removed
 * Remove all legacy code including old client, repository_tool, repository_lib